Fascism is innately an ideology that transcends definitions of "left" and "right". Although it's up for debate whether they were more left wing or right wing, their ideology is a mix of elements from both sides of the spectrum. This isn't my opinion. This is established fact. If anyone tries to tell you that fascism was completely 100% left-wing or right-wing, just tell them to actually look it up on someplace that isn't Conservapedia or RationalWiki.
As for being against AntiFa, of course I am. It's okay to disagree with Trump, and it's perfectly fine to hate Nazis, but they go way too far, are extremist and violent, and see Nazis and Trump supporters as one and the same, and see them everywhere.
In short, even though they aren't truly fascist, they're extremist nutjobs who like to hit people, and thus, 'part of the problem' is putting it lightly.