I'm not hating, it's just not my thing. I sometimes might not understand why someone might like something, but if they have that interest, that's ok. I like going on imgflip, but it's not their thing, and do I care, no, do they care, also no.
If you have seen this scene from the movie in context, it would make a bit more sense. Basically Toothless is dancing and the Lightfury is confused, and Hiccup is giving Toothless a thumbs up. I hope that this helps :)