What do you think about me wanting to insult my friend's lazy eye?
That's hurtful to do. Why would you want to hurt him?
I think he really does have a lazy eye and it looks stupid.
It sounds like you're not very tolerant. It's wrong to make fun of people if they have a medical condition, especially if they are your friends.
What? Noone can tell it's a real problem.
It's wrong to make fun of your friend's lazy eye. This is a medical condition that your friend cannot help. You should consider how you would feel if you developed this condition in the future.