If you judge a man by his actions, probably.

The FBI has been classifying them as a domestic terrorist group since 2015. To respond to Cicero, it is the Intelligence services that classify terror groups, not politicians. Your fears are unfounded (it should be noted that despite many left-wing politicians attempts to brand the Proud Boys as a hate/terror group, the FBI has come out and said they do not classify them as such), and it is extremely useful to be able to classify groups based on their actions. If there was a branch of ISIS in America, you'd want to be able to point the finger and say "terrorists!".

Aren't they already classified as a terrorist organization?

Hopefully not. What kind of precedence would that set? Would domestic terrorist groups come and go with different Presidents? Would Americans be sent to Gitmo? What if Ocassio Cortez is elected President and she declares the NRA as a terrorist organization for promoting the sale of scary child killing machine guns?

How about this, when antifa punches you because they think you’re a Nazi, punch them back until the threat is nutralized. Handle it the American way, don’t run to daddy (government), and have them make more rules and limitations on our liberty. Just beat the living shit out of antifa, problem solved.