The guy who spoke to his son exclusively in Klingon wasn't a Trekkie, he was a computational linguist; his interest was in language acquisition, not Star Trek fandom. The kid never even saw an episode of Star Trek. He was specifically interested in Klingon because of it's limited vocabulary and grammar.
Any sufficiently large group has it's outliers, zealots, and weirdos.
Raw-foodies / fruitarians are the weirdo subset of vegans. Flat-earthers are the weirdo subset of Christians. Sovereign Citizens are the weirdo subset of Libertarians. White Nationalists are the weirdo subset of Conservatives. Parents who speak exclusively to their kids in Klingon are the weirdo subset of Star Trek fandom.