A high-school friend of Nick has been quoted as saying that Nick supported this administration and believed in the war. Also, there was an article which quoted some of the emails that Nick sent to a friend, and some of the things Nick said in his emails indicated that he believed liberating Iraq was right.
Even without those though, it would be strange to believe otherwise since there's no evidence to the contrary.
Finally, Nick's politics don't matter. AQ killed an American citizen. That's what matters.