People hate what they don’t understand. Doesn’t help that it’s hard to study kinks and fetishes since you’re basically asking people to talk about confusing personal sex stuff and sex is considered at best impolite to discuss and at worst shameful. I think @thatkindoffangirl made mention of starting a blog about kink if I recall right and has stated some very good, smart things about kink, especially IRL kink (as opposed to just what stories one reads or pairs they ship), very interesting.
How…? Like, a kink is something you find sexually arousing. In Claude’s case, saying they’re an underage kink-haver means they’re aroused by underage people (Basically they’re a pedophile).