I've been told by people who work in his office that he voted for sanctions (on their central bank not on medical supplies and things of that nature) so that if it comes down to him having to stop the war by himself with a filibuster (or at least force a declaration) then he will have the political capital to say that he's been going through the "diplomatic" steps (because even though we know sanctions lead to war -- in the media they are portrayed as ways to prevent war). If he doesn't vote for any sanctions the perception is that, "oh well you tried to sit by and ignore it and because of that now we have to go in."
Again you may not agree with his tactics but his ultimate goal of preventing war and the fact that he's not voting for sanctions on medical supplies and food, etc. are what we want in a U.S. Senator.