Some monsters can cast Protection From Good and Evil, such as an Orc Hand of Yurtrus. By spell name alone, this seems like it would be useful against a good-aligned party.
The spell description, however, states:
one willing creature you touch is protected against certain types of creatures: aberrations, celestials, elementals, fey, fiends, and undead.
Unless those are just examples of creatures it can protect against, and not a full list, it doesn't sound like the spell offers meaningful protection against, say, a halfling paladin.
Is it just broadly assumed that Protection From Good and Evil will work against PCs, when cast by a monster, or have I missed something?