Seriously, I personally believe that the only people INTJs should ever open up to, are other INTJs and INFPs. When an INTJ opens up to me... I'm the one that's overwhelmed. They're too sensitive in ways I can't understand, especially since their emotions are so unique and personal to them, and thus don't appear on my Fe map.
Not only that, but depending on how long I knew them before, I might have to get over my resentment at realizing that even though I looked up to them for their strength, they're really so much weaker than me. Trying to accept that their show of strength was nothing but a paper tiger.
Essentially, I don't think FJs or TPs have the right kind of awareness or sensitivity to handle an INTJs emotions properly, and will likely just scar the poor creature.