I feel Bob was being a little too black and white on this issue. There are definitely people who do this thing, and several people who make offensive jokes are in fact @$$holes or bigots, but not all. I think it's perfectly possible to make offensive jokes or observe that sometimes politically incorrect assumptions have some element of truth to them.
I agree that Carlos Mencia is a joke of a comic. And that hurts for me to say, because I'm Mexican-American and as such want to see other Hispanic Americans do well. But he is terrible. He is the living embodiment of everything Bob seems to be hating on this week, and is stupid enough to tell you as much. Jeff Dunham is just not very funny.

Seriously Jeff, I liked you the first ten minutes, but you really should've quit while you were ahead.
On the black Thor character, I'm against Bob. If you are indeed fighting FOR political correctness as you claim you are, and fighting AGAINST people who say "oh, you're just being PC," you will realize that there are no black Norse Gods. I have no problem with a black Spider-Man or Captain America because their "whiteness" is not central to their character. The fact that Spidey is white doesn't define him, so if a black, asian, or indian actor does a great job playing him, I'm all for it. But the Norse Gods are WHITE. That IS central to who they are. They are the WHITE gods of a WHITE people. This is one of the very few instances where a character's "whiteness" IS central to the character, so to make him any other race, IS in fact politically incorrect.
As for black Nick Fury, there is a more subjective topic that someone brought up. I personally think white Nick Fury is better. When Fury is white, he's tough as nails, gritty, and in your face. He doesn't take your crap, and he won't hesitate to tell you so. For some reason, black Nick Fury didn't just get a color swap, he got a personality change. Suddenly he's a smooth talking bad-@$$ mutha... etc. I'm not okay with that. I think it defeats the purpose of political correctness if you make a white character black for diversity, and then change that character's personality to match that of walking stereotype Samuel L. Jackson.
I guess my biggest problem was actually Bob's defense of a black Norse god, because as much as I don't like agreeing with people that would appreciate my support then call me a spic or wetback, they're right. Norse gods were white, and that's important to their character.