Depending on the age of the gentleman next door I guess I would bake him some cookies but keep my door locked at all times and develop situation awareness which means keeping your eyes wide open…even as you sleep. It is unfortunate, but the world is full of odd or poor behaving individuals.
I would also think that having ‘a weapon’ on hand would give you a measure of comfort, too. A good squirt gun full of ammonia is a mighty deterrent!!
I think that most people who are obnoxious and difficult are seeking to have power over someone or anyone that can be intimidated. Woman are guilty of this, too, but we generally just call them 'snarky. Learn to let most of such attitudes to roll off your back and learn fast. Meanness won’t kill you but lack of awareness can bite you around the ankles. AS the other poster, said, “Kill them with kindness,” add a high dosage of prayer, refer all wounds and bobos to our Lord and carry on.