Logically, I don't see much of a reason for it, except that perhaps people get too emotionally distraught over our cold humor? Maybe we're a bit biting in our wit, but I don't think we deserve the reputation of being cold, hostile, completely emotionless, analytical, and evil.
Slightly cold, a bit maniacal, repressive, controlling, logical, maybe.
I think it's because they misunderstand INTJs, and have trouble respecting their need for space combined with confidence and bluntness.
ExTJs are more accepted, and ISTJs get things a bit easier because they're less confident.
INTJs make wonderful friends, for as long as you can continue to prove yourself worthy of their friendship. Quite fair, I suppose.
I've liked the INTJs I've known. There is something easy about the interaction overall. I prefer people who behave in a coherent manner and the INTJs I've known share this ideal. Their communication style is more direct than mine, but I appreciate it because I don't have to read between the lines. I can trust their words exactly as they offer them to me (in the instances from experience).
INTJs are one of the types out of step with the norm and often okay with that. They also seem rather resistant to being pressured or manipulated and that probably frustrates some people. They are too independent to be pressured into X by the norm.
There is also that aspect to MBTI that finds a way to berate every type. INTJs probably do get it more than the other types in some ways, but there are certainly some ripe and delicious attacks on most all the types.
The first man to raise a fist is the man who's run out of ideas. H.G. WELLS
The first principle is that you must not fool yourself, and you are the easiest person to fool. FEYNMAN If this is monkey pee, you're on your own.SCULLY