because a lot of rap contains bad language it is looked down upon.
That's just a one sided perspective. I bet 90% of people who say that, swear themselves; thinking they are being rational when it's just hypocritical.
It's not rap that bad, people just look for excuses to bring it down. It's not the rap that is bad or a problem, its those peoples minds that can't accept it.
I like this line off Rabbit Run:
"I’m make you hate me cause you ain’t me,
You aint, it ain’t to late to finally see,
What you close minded fucks were too blind to see"