There is a line there. I can't set fire to your home and call it art to avoid punishment. Why should I be allowed to figuratively set fire to your corner of the internet in the name of art?
You realize that Github pretty much did exactly that with the repo, right?
It was a silly, somewhat mean-spirited project, but it lived in its own dumb little bubble and didn't hurt anyone who didn't choose to go there and be outraged.
They did not set fire to anything. They repudiated their relationship with something.
Compare them to a bookstore. Say the bookstore sends some books back to the publisher (without saying why, but maybe the owner didn't like the paper or something). The bookstore might not be a very good bookstore, but it hasn't burned any books.
Anybody hosting the only copy of anything on Github is making a mistake, so it isn't fair to use an analogy implying that they destroyed something.
Given that Github is now big enough that Google is hosting their code there, I think that view needs to be a bit more nuanced. Yours is a very slick reply that could easily be a boilerplate one for, say, privacy concerns with Google -- "Hey, it's their service, they can do whatever they want".
That's fine, but if they subsequently publish a Transparency Report that isn't very transparent about some things, it's probably a good thing to call them out on it. Would you agree?
Censoring art is still censorship, even if we care for neither the art, the artist, or the message.