Don't know if they're fake or not, but the ones that are ego tripping and really really happy to have been typed as INTJ and really want people to notice their genius. Same with INTPs. And ENTJs. And probably others...You're not terrifying at all. The only people who think that are the fake INTJs who just want to cling onto and promote the stereotypes of the type, people who are only joking or people who think a whole type acts the same way entirely.
I think its a misconception that NT types are scary. Personally, I believe non-NTs are just unenlightened; they fail to miss the bigger picture sometimes. They can't stand up to debate while they simultaneously refuse to conform to a logical mode of thinking.