I would rather not become friends with someone who is depressed.
What caused you to say that you would rather not be friends with this type of person?
I can't deal with people who are depressed. Their existence gets on my nerves.
Although it can be daunting to deal with friends with mental difficulties, you should not totally discount those people as potential friends. They are perfectly capable of being very good friends, and they might be able to teach you how to be more accommodating and kind.
First of all, why did you even become my friend if I'm so bad?
There are plenty of people out there who are very interesting and talented who have mental disabilities. Just be careful with discounting large groups of people because you could really miss out on a lot of what they have to offer.