We have a new pastor, Jay Zaremba, and last Sunday he referred to himself during the service as a "Polack", just in passing, then he caught himself and asked, "Max and Olga [the two parishioners with whom he shares ethnicity], can I call myself a Polack here?"

Ethnic terms are often used innocuously by members of the group but perceived as pejorative when used by outsiders; also, the offensiveness of a particular term can very dramatically from one locale to another or one decade to another. Nowadays, I don't think any Scandinavian-Americans take serious umbrage at "Norsky" or "Svensky", but once upon a time (there was a time when no reputable landlord in Seattle would rent to a Scandinavian — no discrimination involved, just didn't want to have to put up with their language and their boozin' and the smell of their lutefisk — and when businesses hereabouts posted
HELP WANTED
NO NORSKIES NEED APPLY
notices in their windows.

I recall the gradual discovery (by everyone except the NAACP!) of the offensiveness of "colored" as opposed to "Negro >> Black >> Afro-American >> African-American", and the subsequent rehabilitation and reintroduction, with a broader semantic field and heightening modishness, of "[people] of color".

One can't rely on a group member's evaluation of the situation, either. Most of the Eskimos I know call themselves Eskimos; but a few make quite a thing of anglicizing their proper terms, Inuit etc. Likewise some Basques are big on making sure their ethnonym starts with E... People are funny, and so are peoples, sometimes...

Liland