Even so, being OK with that sort of thing for that sort of reason requires believing in collective guilt.
What do you mean by that?
I don't. I believe people are responsible for their own actions, and to some extent responsible for the actions of those directly influenced by them.
I agree, but I think action is a more difficult category than it seems. I always like the example of a kleptomaniac: how can you tell how much of a kleptomaniac's theft is because of his/her moral choices versus some kind of compulsive or non-volitional behavior? We might be willing to say that's an exceptional case; but I think that recent research into the brain suggests it probably isn't as exceptional as we might think.
Basically, I don't think we should let people off the hook for their guilt because someone or something heavily influenced them or conditioned their choices. At the same time, I don't think we should despise people for things we would only pity if it weren't their choice. I don't think a divide between choices and non-choices (nature and nurture?) is helpful.