For people who don't see what's wrong here. The issue is not about whether the word 'retard' is or is not offensive to anyone. You need to consider that GitHub currently hosts a large percentage of the web's open source repositories. This is censorship plain and simple, something that IMO has no place in open source. The issue is that there are plenty of things some people might find offensive on GitHub but you dont…
What's the big deal if Github did delete the repo data from their servers? Isn't the whole point of Git that you can just go and setup an upstream somewhere else with a one-liner? They are merely a free hosting provider among many.
This is not a dispute against the government, so the discussion about censorship and the rights and responsibilities entailed by free speech isn't relevant at all. Remember that the free speech provision is primarily intended to be about citizens' ability to self-organize to defend their constitutional rights if their representatives don't have citizens' interests at heart; it's not meant to be used as an excuse for immature behavior.