I'd say he probably was an INFJ. My reasoning is that he made his ideology a priority over everything else in his life, and amidst the moral and economic confusion of the Weimar Republic, people responded to that. The only problem was that his ideology was extremely flawed, and his desire to create his twisted ideals of beauty out of what he deemed to be decadence ended up destroying the world. He had lost all of his sense of humanity. Until I read Mein Kampf I can't say for sure.
"How dreadful!" cried Lord Henry. "I can stand brute force, but brute reason is quite unbearable. There is something unfair about its use. It is hitting below the intellect." ~ Oscar Wilde - The picture of Dorian Gray