In the case of Crusaders, you have the very people who are being described making the choice for that usage, I don't see a problem with it. They are self-identifying with the term, which is pretty much the opposite of Redskins. If a Muslim school wanted to call themselves the Jihadists, they're free to do so. I doubt they would attract a huge fanbase here, but it's their call. Would I, as someone who's Jewish, go and start a team named the Jihadists? No, I think that would be pointless, but still probably not even as bad as Redskins, just because the word "jihadist" actually has some type of use beyond pure hate. The issue isn't that some terms are offensive, because if you look hard enough, any term can be offensive. The issue, as I see it, is that you have a word being used by one group of people that has no purpose other than to denigrate, and the people who it denigrates believe that is not an appropriate name for them to use.
Dick.