some of them are simply names of groups. I have zero problem, personally, with mascots like the Scots, Seminoles or Utes (other than my irrational sports hate for the program). They aren't being portrayed negatively. It reminds me of the Office skit where Michael asks Oscar if there was a less offensive term than Mexican and Oscar points out it isn't offensive
Even the ones with the negative connotation of "fighting ____" isn't necessarily saying that that group, as a whole, are fighters.
Also, adding the Missionaries weakens your argument.
He should be able to keep the name if we suddenly start accepting mascots like the Darkies, Yellowmen, Brownies, Crackers, etc