[JoshTriplett]

Those aren't typically derogatory descriptions of people, though. Profanity isn't necessarily an issue; derogatory language is. I'd expect Github to take down repositories containing slurs of any kind, while leaving up things like https://github.com/nvbn/thefuck/

[Asbostos]

That doesn't explain why they were seemingly allowed to replace "retards" with "gits" which is obviously still being used with the same derogatory meaning.

[waterlesscloud]

It took me about 1 minute find other repositories using derogatory descriptions of people. I didn't even have to use my imagination.

[JoshTriplett]

And it would take you another 2 to report them, and github a few moments to act on it. They don't necessarily proactively search for it, they act on reports.