I don’t know, my guess is they got away with a lot because of their academic connections. I think Piven wanted to get arrested for publicity—she signed a petition refusing to pay taxes over the Vietnam War in 1968, and she participated in a post-settlement strike at Boston University that almost got her dismissed along with Howard Zinn, who was one of the CP’s key academic contacts during that period and was her colleague. Zinn had some pretty high-powered legal connections to the same lawyers defending the antiwar protestors, I would think Piven would have turned to those resources in event of an arrest.
You are probably right.