Sports fans/ultras are just an expression of the existing sentiments of the community they come from. Racist fans aren’t born in a vaccum, they do however display their beliefs very openly and publicly.
Not all of them are right-wing. Here are some examples of non-reactionary clubs (I don’t know if all of them are specifically leftists):









The amount of fake stories like “my boss was a huge piece of shit then I punched him and quit and everyone clapped then I got a job making x3 my old salary” was very fishy.