A lot has been said about the "emotional blindness" of INTJs and as a strong INTJ, I have yet to find such a fault in myself and from observing many, admittedly historical INTJs, I think that INTJs do possess a great degree of emotional intelligence. You can look at "emotional intelligence" in two ways: either as the ability to think calmly and in a focused manner under pressure, which is purely self-related, or, as the ability to perceive and assess the emotional state of another and influence it, which is a social definition.
As to the first, I think it is axiomatic that INTJs think lucidly under pressure. So the second is the decisve definition. I think of Hannibal, the great Carthinginian general, who wielded a multi-national army and held it together, obedient to his will and fervently devoted to him, a thing which arises not by accident but by policy. How many times, looking at someone, can you, in second, say, "Such-and-such-a-one is such-and-such-a-person" or that they are feeling such-and-such an emotion and that by doing such-and-such a thing, you can influence their emotions in, yes, "such-and-such" a direction. A look, a movement, a word.... All these things give a person away. Is it possible to study emotions using reason? I think so. I am a good judge of people and this has come about through the use of applied reason. Whether what I know comes about with reason used a priori or a posteriori, is unimportant for now.
What INTJs suffer from, is not "emotional blindness", but "emotional inexpressiveness", but this is something which they can get past, to a large extent, but I think it mainly comes about when there is a logical reason to do so: rallying the troops à la Hannibal or Napoleon, gaining some advantage from someone which requires an expression of feeling, though this is limited by the INTJs sense of....honesty....
One does not become a great leader without emotiona intelligence and INTJs do make excellent leaders.
Why do INTJs distrust people, or, wear gloves, as it were, in their presence? Is it because of a sense that there is something inherently threatening in them? A gathering storm? Is it a "matter of hygeine"?