(1) I'm not a famous rapper.
(2) They refer to oral sex as "getting brain" and that's super gross.
That phrase is the most terrifying imagery ever used to describe a beautiful act. Sure, it gives rappers the ability to make brain related puns—"That explain why I love college / Gettin' brain in the library 'cause I love knowledge / When you use your Medulla Oblongata" (Kanye West - Make Her Say). But is it worth the cost? That's a good line, but it sounds like he's lobotomizing this poor psych major who was so kind as to blow Kanye in the study room.
The Medulla Oblongata reference is especially disturbing since that part of the brain regulates the autonomic nervous system including reflex centers for vomiting, coughing, and sneezing. Gross, Mr. West. Gross.
I've never been comfortable with songs that describe sexual encounters anyway, but there's something so graphic, so unpleasant, about brain. Brain. Ew. Why would you want to imply you're poking her in the gray matter? That's so dangerous. It's like your erection is keeping you from thinking and making it so she can't ever again.
And yet they do it so casually. "I'm in the backseat getting my dick wet / I fell asleep getting brain that's a head rest" (Big Sean - Money & Sex). She's not going to be able to do math anymore and you can't even stay awake for the whole thing. Have some pride.
That casual meanness is part of a deeper problem in the genre. Plenty of people have pointed out that rappers are horrible to women and gay men, but what I don't get is why they're burning both those bridges. If you're as into getting blowjobs as you say, you need to get at least one of those groups on your side. No matter how much it costs, your Maybach can't blow you in the library. And if it could, you'd just poke through the engine block anyway and ruin it for everybody.