That's a good thing.ISIS is a crazy terrorist force which is brainwashing the minds of people. They need to be stopped ,and it cannot happen overnight. USA is doing a noble thing by backing up the Kurdish clan.
To be acting nobly seems to me you're acting altruistically. I have no doubt the US offensive against ISIS is rooted in self-serving interests. Maybe they are accomplishing something good (that's up for debate) or they may just be acting out of a sense of responsibility for having done so much to strengthen ISIS in the first place. Either way, I wouldn't call the actions "noble."