An interesting question.
Can a misanthrope be a good writer? It seems like the answer is yes, but that brings up the question, if you don’t like people, who are you writing for? Even if you are writing for yourself, if you are a writer, and try to get publishes, you must be trying to communicate. But what will you have to communicate to people you don’t even like? Why go to the trouble of writing stuff down at all? It’d just be easier, and quicker, to think it all.