I think I understand your frustration. For example, people all over the world are worried about the environment and often want to protest certain governmental policies. So they decide to organise a protest, let's say about a new governmental building. Then organised groups appear and infiltrate the movement and take ownership and along with "save the environment" they will add other demands like "refugees welcome" and "kill the fascists", and if someone says that these are irrelevant he gets a beating. Or if other groups with different political affiliations appear, they get a beating as well. Finally, good people get enough of it and say something like "fuck the environment, I'm out of here" and never return.

However, if behind the governmental policy is someone related to the left with connections to these groups, they will say it's not bad for the environment and why should we protest? They might even organise a counter-protest to beat the shit out of the protesters while the police looks away.

The way things have turned, you can't salvage it. Maybe what's happening is new to US, but has been the norm in other countries.