I am an individualist, and I don't think that "longing to be different" is necessarily individualistic. Actually, I'm pretty opposed to being different just to be different. Be who you are, and be sincere about it. I guess as an IJ, I could care less about reacting against society's trends. That would imply that society has somehow gotten under my skin--my tough outer shell. I don't feel the need to seek out ways of being different. I do that naturally and unconsciously.
To answer the question, though, I think NTs are strong individualists partly because they are such a minority. They are born different, but they might not realize that until many years down the line. I think that the combination of NT, as opposed to NF, gives rationals a hard shell and makes them harder to push around or bully into submission. We NTs have our heads in the clouds (N), so we are unlikely to care what the rest of society thinks of our strangeness. Thus, we were born different, we rarely give a hoot what society thinks about that, and we are focused on goals rather than how we accomplish them.