Honestly, as a 19 year old, I've seen people of all political persuasions like or dislike rap. I'd say the majority of people under 30 like at least some rap music. The people who hate all of it are generally either conservatives who like country and liberals/moderates who only listen to a certain type of rock music (I'm thinking of the Arctic Monkeys fanbase here).
Guess what both those crowds have in common? Hint: Look at the makeup of the country crowds and the indie rock crowds.
Both are overwhelmingly white. And there is a large overlap between white liberal and hipster.
If you asked BRTD about that kind of crowd hell say they are pretty much interchangeable, though I imagine to find some libertarians who could be described as hipsters.
You're probably right about that. Though, BRTD seems to overestimate the hipster population especially the "Hipster Christian" population.