I think NTs just think they know what others are thinking. I'm actually very good at mind reading (not literally, but I can figure out that certain people are less than genuine, I just don't tell them I've worked them out). There's another thread on here with a similar theme: www.wrongplanet.net/postt170997.html.
Here's a personal example of an NT thinking they know how someone feels and then showing that they don't get it at all:
Before I had my daughter, I had 8 years of infertility. My sister-in-law asked me why I never spoke about it, as she knew we were having treatment. I told her that I preferred to deal with it in my own way. She then said, 'I was told that I would be unlikely to have children, so I completely understand, maybe I could have helped'. However, she failed to mention that, 3 months after being given this news, she actually became pregnant, without any intervention. I started trying for a child a few months before her and she had 2 children (7yrs and 2 yrs) by the time I eventually had mine. I don't think that 3 months of thinking you might never have a child can possibly equate to 8 years of infertility and fertility treatment. Yes, I'm sure it's possible to have empathy for someone even if you haven't experienced it, but her 'empathy' was totally off-base.