So when he was smiling while hugging Gamzee, that was really a sign of immense dislike or something...?

Also, I'm pretty sure you can like someone and still acknowledge they're dangerous, probably especially in Alternian culture. Also, for all his flipping out rage caps, Karkat is pretty well grounded from what I can tell. Of course the phrase "He's dangerous" is more important than "We're pale".

...Usually.