What is the best way to deal with someone who always feels the need to be argumentative and controversial?

You need to do what everyone else does and get away from him. The problem with narcissistic personality disorder, is that in their mind they don't have a problem, you do. In their mind they are God like, like saints, great egos. In their mind they are right and the world is all wrong. They are experts on everything, and they are experts on putting others down, bullying them. They are incapable of taking responsibility for their actions and behaviors, and incapable of changing, because in their mind they are right and the world is all wrong. Stay away from this person as much as possible.