There's a lot of propaganda, indeed. But that goes for both sides. And it isn't exclusive for Syria.
Truth be told, I haven't really studied the Syria situation enough to really make the call who's right or not. But what is certain is that the situation right now in Syria is pretty fucked up, and the way the country has been run (and still is) by its elite is undeniably a factor here.
If the Syrian' leaders were having problem with rebellious groups, they could easily reach out for help from the UN, Russia etc, and solve this alleged problem publically. No, instead they just go against they're own population, in quite a brutal way.
Imo, there is no defence for the way the situation is handled in Syria right now.