Makes them violent extremists
Only if you believe that any violence is extreme. I would disagree, punching fascists is fairly centrist and enjoys broad support.
what I've seen, plenty of antifa folk will use violence and vandalism against people unrelated to the supposed target group.
That is besides the point. You can be against facists and also against Nestle at the same time.
Precisely. This is why the EU is harder on these companies.
When you get big enough, there are different rules to ensure that you don't distort a market by killing competition. That is anti-trust, and that is considered a monopoly.