re: Why are all criminals in commercials white?

Same reasons that white men are the butt of all jokes in commercials and any time a character needs to be seen as stupid. Same reason all women who appear as "smart" have on glasses. Same reason now you see more and more bi racial couples instead of same race couples in ads regardless of context. Same reason (but more subtle) you now see more and more gay couples in ads.

its all Politically correct. (bullshite.)