Sure, there's truth to that. Doesn't just apply to a terrorism context, either. I forget which essay it was, but Scott Alexander pointed out that while everyone hates PETA, nobody has heard of the animal rights activism orgs which behave responsibly. Still, even if nobody would have heard of Kaczynski or his ideas, it seems to me like that's better than a world in which everyone has heard of his ideas but they aren't allowed to be taken seriously in polite society because of the association with his actions.