>I guess what I want to know is if fed infiltration is inevitable why be so hostile to forming/joining orgs?
It's not. You have to be pragmatic and smart if you want to stay on the side of the law and accept that rats for the system are always looking to fuck you over. Even if they agree with you, they're more concerned with the benefits the system gives them than any sort of idealism or what has "worked" in other parts of the globe because socialist ideals and how they're put into practice throughout history are an anathema to American ways of thinking and the way of life.
Every fed, even if they could be swayed by reason or emotion, their first loyalty is to the state and protect it against everything their paymasters perceive as a threat. They're not interested in your revolution and be more than happy to crush it if given the go ahead. However, if you're not afraid to do counter-intelligence against them, find out who they are and expose them, they're more than likely going to crush your organization through direct force if it comes to that, but at least you caught them red-handed and embarrassed them in front of their paymasters.