What if I hate you so much so very much?
That's not good. Why do you hate me so very much?
Because you're such a nice guy! And it makes me sick
You don't have to like everybody but you shouldn't tell people that you hate them. It is mean and it will hurt their feelings.
I also don't like you because you are not that smart.
You don't have to like everybody you meet and you don't even need to have many reasons to hate them. But you don't have to tell them that you hate them. It is mean and rude and people will think you are a bully.