It's a joke. Jokes are fine. Jokes about anything are fine, as along as they are jokes.

You didn't think this joke was funny, and that's fine. I thought it was funny, and that's fine.

Calling it a "Nazi-ism", is also fine, but if that means he shouldn't be allowed to say it, that is not fine.

See the following picture, it kinda captures the point:

https://pbs.twimg.com/media/FrrVOoFXoAEOWYe?format=jpg&name=...