I don't see it as being racist at all. They don't have the same negativity with RG3 and its all about attitude. RG3 comes across as humble where Cam comes across as arrogant. That's why he gets so much grief. I'll still take Cam over RG3 any day. He is just on another level in my opinion.
We can't expect every black QB to behave like RG3 to be 'accepted' or not given the due respect. In fact RG3 makes it easier to poo on Cam because they can always say "They don't have the same negativity with RG3 and its all about attitude".