For what it's worth, I recall an ethical argument by him at the ZNet forum along the lines of (too difficult to search now):
You share responsibility for an action's predictable consequences, in the proportion you're able to participate in its decisionmaking. Since the US is somewhere between dictatorship and true democracy, US citizens share some responsibility, particularly the more privileged ones.
However, if this abstract argument is sound, I don't take it to imply that anyone here is supposed to feel differently, change their actions or slit their wrists. Certainly, a "responsible person" is someone who has responsibilities, and acts with integrity in relation to them.
Tayssir