Insofar as many poetic forms throughout history are properly performed (rather than read) and that many examples are indeed sung (one sings the Qu'ran, for instance, for full effect, and what are Gregorian Chants if not early rap?) leading up to the age of the troubadours, who "sang: their alliterative and stanza-centric "news" wherever they went, rap certainly does fit in that ambiguous area between what we call Music and simple poetry. That said, Sturgeon's Law is even, more in force than in other forms, it seems, and 95% of it is crap. Too much of it is used to express anger, but why should that garner indignation, especially from those of us for whom Won't Get Fooled Again was a cultural battlecry and Time (Chambers Brotrhers) an anthem?
I don't like rap. The backing tracks are usually too damn loud and compete with the lyric content, which is the whole point of the form, so it comes out to my ear as an atonal mush. But as I've said before, saying you don't like something is not the same as saying it's bad. Other standards apply.
Okay, rappers use turntables for backbeats. There's a whole industry in the field in "beats" which apparently are identifiable with certain rappers. We've moved way past the days when two discarded turntables were wired into a portable sound system and now those DJ rigs cost almost as much as a keyboard array, so let's stop this "po folk" nonsense. If that were the case, then no poor black person would ever have made music before the advent of rap, "'cause all those instruments cost too damn much and I got no bread." That's bullshit.
Rap came out of a recognition that "message music" has one drawback---the music tends to mute the message, especially if what you want to do is harangue instead of sing. Street games like Dozens fed into it and a form was adapted to a new kind of dance performance, which in many ways is a modern African American adaptation of the square dance call. It was fun and became marketable and now we have what we have.
I don't like rap. But I also don't like opera. Are they comparable in any way?
What gets hard is to remember that it's personal taste and that, unless we're trying to proselytize, is not really open for analysis. Right now I'm listening to Juno Reactor. I really like their stuff, but it's not much more than a set of complex beats with a thin riff overlay. At least on first listen. I'll admit that a lot more is going on that is not immediately apparent. The same can be said for rap.
But we get into these long digressions when someone tries to make something more emblematic of more things than it can bear.