An argument that I've used effectively at several hotels in the U.S. is- if there are no signs at the pool or jacuzzi stating "No Nudity", then we assume its OK. And we use discretion when going nude so we haven't gotten any complaints yet. That being said, many parts of the U.S. still have very puritanical ideas regarding nudity. Unfortunately many in the U.S. equate nude with lewd.

Many European and Asian countries are just the opposite. Germans are very accepting of nudity and actually have legalized nude hiking trails. Many onsens in Japan require nudity.