I Hate My Job

I'm just starting to notice how ugly my workplace is. My boss has always been nothing but pleasant and kind to me, because he seems to like me. But it doesn't matter when I see how he treats coworkers he doesn't like. Essentially I've come to see how there are people in his "circle" who get better treatment and people outside the circle whom he condescends to and doesn't respect. And in some cases, he freezes them out until they quit in frustration. At first I thought I was overreacting but now I see this is how it really works here. In fact, I suspect that part of the reason my boss likes me is because I don't speak up. And those who actually voice concerns and come up with ideas about how to improve things get put on his shitlist. I don't know how much longer I can work here.