It depends on the character. Many of the characters in my current game are based on monsters, mythological creatures, or characters from fiction. If I think a like or dislike fits in with the character they're based on, I agree to it.
If it has nothing to do with the character, I might let them have a like if it's a useful skill, but might just click "no" so I have more time to think about it. If they want to dislike something , I am more likely to say "no", because dislikes tend to stress them out. The stupid sims will go off and do things they don't like, and then get stressed out about it. So I protect them by giving them very few dislikes. LOL As I said, though, it depends on the character.