You have to divide the ideological conflict between individualism and collectivism into 2 lines to make things clear.

First, there is the question of “in political matters, which group should I rally around to fight for my interests?”. There are many possible answers to this: Nobody, a national group, a gender or racial group, a class. Of these answers, only “nobody” qualifies as “individualist”. And yet, when one frames it with the question I have used, it becomes obvious why the “individualist” answer is frankly, idiotic. You have a better chance of winning a fight when you have numbers on your side, plain and simple.

This question is often conflated with the other line along which the conflict extends. “Should I act to prioritize my own interests or those of my preferred groups?”. These are 2 different questions, and very often, people choose to be “collectivist” for the first question, while choosing the “individualist” answer for the second. In fact, this is often the core of reactionary politics, in which selfish people rally around national, racial or gendered groups to preserve their privilege.

The answer to the second question depends entirely on who you are as a person. Everybody has differing limits on how far they are willing to go in self-sacrifice and under what conditions. This depends on you as a person, and I don’t think reason or philosophy can really change that all too much. However, being willing to undertake self-sacrifice for a group does not make you into a “subhuman insectoid creature incapable of thought”. I have a conjecture that some people mock self-sacrifice like this because of insecurities. Instead of simply accepting their own selfishness and living with it, they make excuses about why it is infact morally good to be selfish. I honestly find that amusing. Acting self-centered but still seeking validation from others.