If he paid for that name (assuming it was a name change) then I think he should just be given a free one to change it again. If that is an old account with a good amount of experience I once again think he should be given a name change. Because like the first post said, it's just a name in the end, it shouldn't be a problem unless he's literally acting like Hitler and being offensive to jews and blacks on the game.
just told to
Well, the most popular reason is that there are still people alive who were tortured/affected by Hitler and for them it's inappropriate to use such a name. Like imagine you lived in the 16th century in Novgorod and have like your whole city tortured to death by Ivan the cruel. Wouldn't it be nice to see someone with the exact name some years later (not regarding the habit of such a person)? No, it wouldn't. If you pick such a name, it's just offensive and you should know that.
Oh and it's quite simple why god isn't inappropriate: it's not proofed that he even exists/existed. Like you said he's have done such things.