There was widespread international anger over the Bush doctrine and the unilateral American invasion of Iraq, supposedly in an attempt to stop the spread of weapons of mass destruction. Multi-lateral diplomatic missions are much more successful. Right now, Syria is voluntarily dismantling its chemical weapons stockpiles as a result of diplomacy.
This action will increase anger towards the US not only anger the country that don't like us, but those that are on our side (as it is a unilateral action). In addition it is hypocritical- WE HAVE NUKES TOO, why can't others? The way I see it, it isn't our duty to dictate the world.