It's dongle-joke between two friends in the open. Who the fuck are you to act on that? I don't mean you personally, I mean in general.
Don't compare this to racism or hate-crime like someone else did. That's just watering down words.
The fact that this got into the HN front page and received hundreds of comments means that some people do care and this is an actual issue(?), censorship or what not.
Which is sort of my point. You never know when your repository will become popular for reasons good or bad, but it will reflect on both the author and GitHub.
GitHub will probably get the flak either way: for censorship if they try to force the author to change it, or they might be seen condoning the behaviour if they do not do anything.
Just an aside. I'd like to think that anything people put on GitHub is going to become somewhat like public record. It will stay there long after the project has been abandoned.
If it's just a commit message, then I can see why you would think this construes as a `private` conversation (i.e. message between committers). But, it's also in the README which, by default, the first thing you see when you open up the repository.
The better analogy perhaps, is the author is standing with a signboard containing some offensive language in some corner of a public space.
Now there's an unwarranted assumption if ever I saw one ;)
Of course, I can see that this is done for laughs, but not everyone sees that.