For me, rap is fast-talking, not really singing because it doesn't require any singing ability or vocal range. I like rap but I don't like American rap. Rap exists in other languages as well, and I prefer it in things like Korean and Chinese (because I can understand it too and they don't use curse words every second sentence).
I really only have something against what (most) rap is promoting: Sex and Drugs.
That's also one of my main gripes with rap. Not only do I find most rap songs painfully repetitive, I don't get why they can't talk about something else. I'm not saying every single rap song is about the same thing, but the majority and the most popular ones are about the same thing.