Because the differences are only aesthetic. It's important for society to train itself to remember that fact.
Racism is very much still a real thing and causes a great amount of suffering & inequality. Do you really think we should relax our fight against racism for the sake of a bit of "light hearted banter"?
Yes I do. Comedy and not taking our differences so seriously is one of the best ways of bringing people together.
All this clap-trap about everyone being the same is clearly bollocks, we are different and that should be celebrated rather then pretend otherwise.