idk about where you guys live, but where I live jews have a bad rep for being cheap. there aren't many jewish people where I live so it can be easy to talk out there religion. Its is also used as an insult, WW2 propaganda in German gave Jews a terrible look that wasn't true but is still accepting by some people today (example: Big noses, or little hats, or bald) these are all things can be used as a harmful term.
As for trump, people were using the term too much in eggwars when someone placed a blocks in an order that remotely resembled a wall, it was becoming an insult so cube banned it, simple as that.