The Proud Boys on the right are supporters of authoritarian rule. I think the authoritarian left represented by the Sanders camp are quite possibly on the same wavelength as Trump's Proud Boys. We've even seen posts from that element of the left saying that Trump was the best thing that could have happened for them. Also posts from Sanders's so-called Progressives decrying "suppression of free speech" and acts of self defense when fascists go after people who simply won't step out of their way. Anti fascists are as anti-authoritarian as they are left. There isn't any intersection of interests between the authoritarian right fascists and the anti-fascist. Not in Portland, at any rate.
I don't think it would be helpful if anti-fascism became militant and planned to carry out violence like the radical right are doing. I agree that escalation of violence by anti-fascists would end badly. Fascists are already escalating violence. I think that is going to end badly too, once Trump's political cover for them is blown.
I have mixed thoughts about what you described in St Paul in the '80's. At that time, the status quo wasn't supporting neo-nazi skin heads like it is now. The battle for the streets that is said to have taken place wasn't nearly as political as it is today. So, it's an echo from the past you are hearing and not a direct comparison.
We are taking criticism from all sides, left and right for standing against fascists. I don't understand why the center or left are doing so. Our tactics are working. We foiled fascist plans to escalate violence, we have a Mayor who sees the writing on the wall if he doesn't work with us to stop the violence both from the goons but also the police. Oregon has very strong constitutional guarantees for free speech and Wheeler has yet to find a legal way to prevent permits for these events. He has made some attempts but the city council hasn't yet affirmed his legislation. I think its just a matter of time before we come up with a legally valid way to stop violent groups like Proud Boys from obtaining those permits. Just days before the goons came here, Portland police arrested three right leaders who caused violence in late May. It seems to have helped this time.
https://www.opb.org/news/article/portland-oregon-protest-ordinance-ted-wheeler-city-council/
Arrests precede major demonstrations in Portland, Oregon