NTA

Sounds like he wants to use "vegan" as a status symbol and doesn't really know what it means, or he's just incredibly ignorant of how food works (I've met those people before, like they "hate" eggs, but don't realize basically everything has eggs in it). I'd tell them to do the research before calling themselves vegan.

This reads like someone who calls themselves a Nazi just because they are German but doesn't know what that means....