I think there is a general trend away from using noun forms for ethnic or national groups toward using adjective based forms. Instead of calling somone a “Frenchman”, “Briton”, “Spaniard” or “Dane”; in everyday usage, we tend to now hear adjective based forms such as “French, British, Spanish, or Danish people”. I’m not saying the nouns are no longer in use, but that’s the general trend. I think “Jew” vs. “Jewish person” may be part of that - but other factors may be at play.
On a related note, is it rude to refer to people as “blacks”, as opposed to “black people”? I don’t sense that sort of dichotomy when refering to “whites” as opposed to “white people”.
I always get the impression that calling a native of Spain “a Spaniard” is insulting. Also, someone from Scotland takes offence if they are referred to as Scotch. Am i right, or have I made this up?
“Scotch” is different because it’s considered an erroneous contraction “Scottish.” In Scotland itself, correct me if I’m wrong, the noun “Scot” is perfectly acceptable, but the adjectival form is “Scots.” Outside Scotland, the adjective “Scottish” is (or was) considered acceptable. Just don’t say “Scotch” unless you’re talking about broth or whiskey. Or unless your name is Robert Burns… O thou, my Muse! guid auld Scotch drink!"