It was a tea party mob. Their chosen candidate stood by. Hate was palpable. Subsequent comments were even worse. But, no, no responsibility there. Bringing up political hate is "divisive," it's "politicizing tragedy." Even to ask the question or to want to have a clear-headed discussion.
Contrast the Congressman's words to those used against him.
Incidentally, here's (in a comment thread) some rich (and satisfying) irony:
Does anyone else see the irony in this tragedy? In Arizona, the state that has been the de facto "face" of recent political gay bashing (DADT-McCain) and Racism (their highly controversial immigration law), a white straight man shoots a member of congress who then has her life saved by a gay Hispanic American. It's poetic.
