Why do people hate President Obama?

I have almost absolutely no understanding of politics. I don't really understand what is a republican or democrat or why they hate each other, or what in the world being a liberal means. Or why do all of these different political groups hate each other. I don't get it, I have met people from all different walks of life, and the deciding factor of whether or not I like them, isn't based on whether or not they are democratic or republican. Anyway, take me for instance, I don't believe in the death penalty, I am pro-gay marriage, I think abortion is wrong, and I desperately want to bring my soldiers home because I am proud of my soldiers, what does that make me? A liberal? Democrat? Republican? Other? I guess I don't understand the labeling in politics, there is no way someone totally embodies what their party "stands" for. Also, why do people hate President Obama? What has he done that is so awful? Or what hasn't he done? I just don't understand. The way I feel, is that every politician is almost exactly alike, and will make almost the same laws, because they are just trying to keep the peace and keep their political funding. Can someone answer or explain any of the things I have brought up? And yes please actually answer my question, don't say it is because he is a democrat, explain why being a democrat would make people hate him, or however you answer, answer it well. Thanks!