I would do excellent in a teaching atmosphere; I'm really good at getting ideas across. Unfortunately, dealing with all the crap involved wouldn't be something I'd have fun doing. I wouldn't like grading either; I don't like work that pours over into my free time ^^;
MLJ: Yes, that's true in some instances, I'll be inclined to admit. I do manipulate people occasionally using guilt and whatnot. But I also know quite a few ENTJs IRL, including my twin sister, and I can definitely say that our type dynamics might be one of the reasons we seem more so to you.
We do have other people's best interest in mind. I can be self-centered, but I absolutely hate letting other people down, and lately I've been working on centering myself so I can stop putting myself in stressful situations for others. I like being helpful, but if I am too stretched out between people, I can become emotionally manipulative. It's not so much my natural state; it's actually more of a stress reaction, a brief appearance of the INFJ shadow.
But yeah. We can seem as if we lack direction and are self-centered, but that may just be because many of us don't communicate our desire to see justice in the world, unless it comes up directly. We're not the type that really verbalizes things like that, but we do feel it inside. You are probably more sensitive to this because of your extroverted thinking verses our introverted feeling; it would make it a bit harder for intentions to always be easily understood.
Sometimes it takes some real digging to see our real intentions
I would say that a well-rounded, stressless INFJ are usually inclined to be fair as a natural reaction.