You said "We need those words as much as we need every other word." - and I just proved with three examples that you don't need any certain words in society.
There's a difference between taking green out of painting, and taking out a very very specific shade of green that could easily be replaced with another.
The censored word you used has never been used to describe "African". At best, it was used to describe black slaves. Even then, that word is associated with slavery/lynching/racism. There is no acceptable use of that word in an online video game.
Further, while there are certain words that are acceptable in real life, this is an online video game where you play with 9 strangers each game. You have no clue where they come from or what their life is like. You don't know if they're the people who say the n word to each other daily, or if they're someone who maybe was violently assaulted in an act of racism. You don't know if their parents screamed the f word at them while beating them, forcing them to run away and become homeless, all because of their sexuality.
Words do change over time - but that works in both directions. Words that were considered cursing become more generally accepted. But also, words that were considered acceptable in some cases (f-g, retard, etc) become unacceptable.
