I'm on the Left: My view of them is that they are ultimately counter-productive. I have written about it before: https://steemit.com/sargonofakkad/@pirateofthedtube/antifa-are-complete-and-utter-morons-the-sargon-of-akkad-event

The big points are that they tend to engage in violence when it is not absolutely necessary, which allows those on the Right to point out that "both sides" are an issue. They tend to end up highlighting those who they try to de-platform. They scare people into moving to the right because most people start to think that the radicals/AnComs are a powerful force on the Left. Speaking of AnComs...their ideology is remarkably unpopular and drives people away from actual "anti-fascist action". There are so many ways to oppose actual fascism that many people would be willing to take part in that Antifa does not foster. Instead of reaching out and trying to convince moderates, they just drive them away.