Well, there’s a general tendency in English for nouns to be more pejorative than adjectives. (Hence the tendency to replace them with modifying phrases, e.g. “the disabled” > “disabled people” > “people with disability”.)
With “Jew”, I think it’s related to the fact that this word by itself has been used as a slur. (Slurs in English tend to be short words—often monosyllabic—so another general tendency is that longer words sound more polite.)
But whatever the history, saying “Jew poster” or “Jew actor” or “Jew school” etc. is rude and offensive in English. Just don’t do it.
"Richmond is a real scholar; Owen just learns languages because he can't bear not to know what other people are saying."--Margaret Lattimore on her two sons