having some private funding, shadowy as it may be, is not the same thing as being the official paramilitary arm of a political party and that party running cover for your activities in the highest levels of government. And again, Antifa is not an organized group. They are a collection of groups, organized locally. You might be able to call them a citizens militia if you really wanted to stretch a term.
The Brownshirts were the equivalent of Hezbollah or Hamas. Antifa is nowhere near that.They aren't a caucus in the Democratic party and receive no official funding or state support. The SA did and they were set loose against a great number of people in pre-war Germany, namely Jews and anarchists/communists.
Antifa isn't fascism. It's not even close. You can openly say you don't approve of Antifa, but calling it fascist is nothing but hyperbole.