I’m not sure how true any of what they’re claiming is, but it sounds like typical anti-communist propaganda to blame the Nazis on the Soviets, although there probably is some ironic truth to the idea that Nazism came as a result of a reaction against the Bolshevik Soviets. And it seems that Lenin respected the party for a while until bourgeois elements of proto-Nazism in the SPD were causes of the split and presumably ground for a later collaboration between the SPD and the Nazis, according to The German Revolution by Pierre Broue:

Social Democracy Before 1914

The split between Social Democrats and Communists, the basis for which had existed since August 1914, when almost every socialist party supported its government on the outbreak of the First World War, and which was realised in 1919 with the establishment of the Communist International, has projected a distorting light on the history of the International. Many writers, politicians and historians who have attempted to discover the roots of this significant split treat it as a phenomenon which could have been foreseen. Although the tensions and debates within the International prior to 1914 were implicit pointers to a split, few if any socialists desired a schism. The Russian Bolshevik faction, the nucleus of the future world Communist movement, regarded itself as no more than a Russian faction constructing a workers’ social-democratic party – which in the language of those times meant ‘revolutionary Marxist’ – in the given historical conditions of the empire of the Tsars. When Lenin was polemicising in 1905 against Peter Struve, he angrily denied that he wanted to split the Party:

When and where did I call the ‘revolutionism of Bebel and Kautsky’ opportunism? When and where did I ever claim to have created any sort of special trend in international social democracy not identical with the trend of Bebel and Kautsky? When and where have there been brought to light differences between me, on the one hand, and Bebel and Kautsky, on the other – differences even slightly approximating in gravity the differences between Bebel and Kautsky, for instance, on the agrarian question in Breslau? The indignation of the Bolshevik leader in 1905 was legitimate. Despite many discussions and differences, he maintained this attitude until 1914, and let slip no occasion to pay homage to German Social Democracy, the model of that ‘revolutionary social democracy’ which he wished to construct in Russia, in opposition to those he regarded as the opportunists, whom he wished to exclude from the Party only because they denied the necessity for its existence and wished to ‘liquidate’ it.

…

The Party bureaucracy

The analyses of sociologists such as Max Weber and Robert Michels,24 and the furious attacks by French Socialists such as Charles Andler, have contributed to painting a somewhat schematic picture of German Social Democracy. They tried to explain the victory of revisionism in its ranks by depicting the SPD as a sclerotic, bureaucratised organisation, fundamentally conservative, tightly subjected to an apparatus of politically-limited functionaries, and consequently integrated into the society which it originally claimed to be struggling against and transforming.

There is a real basis for these accusations. The Executive, which had been strengthened at the demand of the radicals in the period of the struggle against revisionism, was dominated by full-timers who in practice were not subject to control. The Executive appointed and paid the local and regional secretaries who made up the hierarchy which contained all the activity of the organisations in a fine-meshed net. Discipline was strict, and the elected members or the representatives in the mass organisations were subject to tight control in the Party fractions which the full-time members of the leadership controlled. The Executive also nominated the candidates in elections, made the careers of the full-timers, transferred functionaries, technicians, instructors and journalists, and conducted the electoral campaigns, which were their main business, like military operations.

Michels explained this complete centralisation of the apparatus and the reign of strict discipline as the result of the victory of conservatism in the ideology of the Party from 1906 onwards. However, these same characteristics led Lenin to regard the German Party as the model of revolutionary social democracy. In his opinion, Bebel and the activists of his generation had realised the aim, which the Bolsheviks proclaimed but had not yet attained, of a disciplined, centralised mass party which would constitute the framework for a workers’ army firmly led by a professional general staff. From this point of view, German Social Democracy was the object of the somewhat envious admiration of the few Russian émigrés who had the good fortune to familiarise themselves with its functioning.

The contradiction existed only in appearance. Carl Schorske remarks in his discussion of the sociologists and of Michels in particular: ‘The purposes for which – and the circumstances under which – the bureaucracy was constructed were far stronger forces for conservatism than the mere fact that the functionaries were salaried.’25 The professional revolutionaries who had built the Bolshevik faction in order to bring revolutionary consciousness and socialdemocratic organisation to the Russian working class did so in conditions of illegality and repression which hardly gave them the possibility or even the temptation to adapt themselves to, or to integrate themselves into, Tsarist society. They had maintained their revolutionary objective, which might have seemed even more remote than in Germany, in the forefront of their general propaganda, whilst they strongly centralised their organisation – yet no conservatism found its way into their daily practice. On the contrary, the apparatus of German Social Democracy, which did not reject in principle its long-term revolutionary objective any more than the Russian Bolsheviks, was constructed entirely between 1906 and 1909. In this period, it was seeking electoral effectiveness, to increase the number of votes won and candidates elected, during a period of relative social calm and reflux of the working class, and it was preoccupied with ensuring that internal conflicts did not weaken its electoral impact, and that the revolutionary phraseology of its radical wing or the demands of the least-favoured workers did not scare off potential voters amongst the democratic petty bourgeoisie and the most conservative strata of the workers. The revisionism of Bernstein and the reformism of the leaders of the trade unions had taken root in an economic conjuncture which encouraged optimistic beliefs in continued, peaceful progress.

This was what Zinoviev was to do his best to demonstrate by means of a study of the statistics which were published by the organisation in Greater Berlin in 1907. He was trying, after the event, to explain the change in the nature of the Party and the ‘treachery’ of its leaders in 1914, and emphasised that, at that date, the percentage of members who were definitely not wageearners – ‘self-employed workers’ including proprietors of inns and taverns, barbers, artisans, traders and even small-scale manufacturers – could be estimated at 9.8 per cent. The specific political weight of these elements was all the greater because the Party was orienting its electoral effort and adapting its language in order to win this clientèle. The counterweight was insubstantial; only 14.9 per cent of the members of the Party figure in the statistics under the simple label of ‘workers’, or to be more precise, unskilled workers, who, in fact, made up the mass of the working class.26

The core of the Party’s supporters was composed of skilled workers who had a trade, whom Zinoviev called ‘the labour aristocracy’.27 It was from their ranks that the Party’s full-time staff was recruited, an apparatus of some thousands of privileged functionaries,28 who often held more than one job and salary, and controlled promotions in the Party’s apparatus – its press, treasury and mass organisations – in brief, what Zinoviev called ‘the labour bureaucracy’. He defined this as a caste which tried to hide the fact that it existed, but which had its own clearly defined interests. Its aim was ‘order and peace’, the social status quo, which gave an increasingly conservative character to the Party’s policies. He drew the conclusion that the members of this caste were, in reality, emissaries of the bourgeoisie within the ranks of the proletariat.29

Carl Schorske arrived at a very similar analysis and conclusions, though he formulated them differently, in his study of the manner in which conservatism seeped into the party:

What the party functionary wanted above all else was peace and unity in the organisation. In the riven condition of the party, this made him a natural opponent of both criticism and change. And as the pressure for change came increasingly from the left, the functionary identified himself increasingly with the right.30