I agree, but I don't want anyone to think blame should be shared equally (not that I think you were suggesting this, but that others could interpret it this way). I also don't think that being complicit in an act equates to sharing blame. There is accountable complacency and unaccountable. This is more why it is important to think about how our work can be abused. It always will be abused, and you'll never be able to figure out all the creative ways that they can be. But that doesn't mean you shouldn't try. Intentional ignorance is accountable complacency. Everything is on a spectrum: complacency, blame, abuse, ignorance, etc. We do need to be careful in how we discretize the bins, and make sure we don't binarize. There's unwilling and unwitting complacency, and that should be accounted for. A lot does matter about how much control you have, as you said. But I also think recognition matters: if you realize that the tool will/is being abused then complacency is more explicit/accountable.
Things are easy to see post hoc, and we can always think "what if." I hope that, given what you wrote, you don't blame yourself. But now you, and others, have better tools to predict potential abuse. After all, the road to hell is paved with good intentions (the road to heaven is paved of the same stuff, which is why it is hard to distinguish).