I hope my cynicism is misplaced and GP has a genuine passion for 18th century maritime history. But most people I meet who "can't help" spewing out random facts are more r/iamverysmart than actual enthusiasts.
Stories like the Longitude story can be told outside academic dissertations - by people like Dava Sobel, though, not really by Fred who's just read her book.
It's not a matter of arrogance, pseudo-intellectualism or anything else. It's a matter of wanting to share interesting things one knows.
The phrase "I explained about longitude" paints a very different picture in my head to "I told my friends about this great book about longitude", but maybe that's just me.
If I don't make any more replies, it's because some people who don't like the tone of my original post are taking the opportunity to downvote everything I say.