I like RHCP too.
I have found too that there are some hints to sex in there. Now, after some 6 years I finally understood what that "Californication" has to do with sex.
Limp Bizkit sometimes tends to get a little agressive indeed but I found that at least some of the songs don't propagate violence. Linkin Park has come across to me as weltschmertz-y music. Also, I read that they don't use "bad words" because they feel that they can get their point across without using profanities. I kinda like that.
I don't know about rappers though because I generally don't listen to rap music...