What is the point of saying "hentai"?

Whenever anime is brought up in a conversation with anyone who has no interest in it, they inevitably respond with "hentai". I see the same pattern online and this post is an example. What is the point of it tho? Are they trying to embarrass us? Prove they know more about anime than we do? Let us know they don't like anime? A mix of all of the above? What do they think they are accomplishing by this?