No, the answer is NOT that art is subjective. I don't think it can be boiled down that easily, but if I were to try and answer succinctly, I would say the difference is there because black people, specifically African Americans, live in a culturally parallel America where there are different rules about what is and isn't acceptable. There is intense pressure on Black men to be "hard" and the way to express that is usually laid out in song.
I actually DON'T think it's his responsibility to be a role model. BUT I think it's wrong to glorify his success without saying something about the path he walked/walks to obtain it. He is 40-something and STILL writing lyrics about selling drugs.
As for citing examples, I'm sorry, I haven't been keeping a running log of the number of funerals I've been to, the guys I've known who've gotten shot, the women (including myself) who've been physically harassed by guys trying to re-enact the latest video, the children who are lost to drug addicted parents, and every other societal ramification that comes from supporting hip hop culture without qualifying/recognizing the damage it does to the black community. I live it, I think that's enough.