I would say you're just as likely to find NTs as NFs in the activism field. Indeed, I've been working my entire post-college life (ok so that's only 4 years) in social justice. For me the primary difference in impulse between the two archetypes are of driving intent:
An NT hears about a social injustice and thinks "well that's really dumb". An NF hears about the same injustice and thinks "that's really wrong". Neither one is more or less motivating/more or less worthy, as they both hit a core driver for each type. My first impulse, however, is less attached to direct service and more towards systemic problems. I tend to need little or no contact with those theoretically being helped by my actions, whereas I vitally need to see that programs are being put into place that will minimize/eliminate the injustice I'm reacting against.
Does that make any sense at all?
I work towards the idea. Not the actual people involved. My INFJ gf on the other hand, is all about individual people. Yet, we still aim for the same resolution even if our motivation is focused differently.
being vegan... i'm around a lot of vegans... and i really would never be able to get into the whole animal rights "movement". I can see why they do/support what they do, but it's not something that is going to play a hefty role in my life. i do volunteer... typically in orphanages... it's hard for me to connect, and i see it as something that benefits me more than the kids... i usually walk away a little more grateful and a little less pessimistic. I've read into "anorexia awareness" groups... but they put me off.. it's a long spiel. I'm more interested in cancer/sclerosis research/awareness/etc. The only topic that really gets me "fired up" is freedom of... well, nearly everything, not just speech... but, overall, i'm so against groups that i would never find myself doing anything substantial for a movement/protest. I could see sense in writing an editorial or even a book... not like I'll ever do that... or an individual tackling something in an innovative way (like Three Cups of Tea)... otherwise, I have no interest and i do not participate.
Libertarians are only freedom lovers if you consider the government to be the only entity that wants to control you. If a libertarian wants to be relevant they should get a time machine and go back a few hundred years.
I can make written impassioned statements for certain causes (why some have thought I was an NF, or at least "write like" one), but these are usually causes that nobody else seems to think about. I try to raise awareness about the issue, and then if it caught on, and others who are better at activism take over, I'll drop it (I wouldn't be good at doing any kind of activism in person). One such issue is the financial crisis, and people out there who've all along thought that the rich "deserve" all they have, but when the economy and their own pockets are drained, they'll actually blame the poor and oppose taxing the rich. I got into this a little bit in the politics section here, and have long complained about it elsewhere.
It's just that something like that seems so dumb of people to just go along like sheep and throw the blame in the entirely wrong direction and talk about who "deserves" what, and this stuff affects us all, and someone needs to stand up and tell the truth and try to make people wise to what's going on. I see it as more of a logic issue than a value issue, though it does tie into values. However, I realize that the solutions or "ideals" on either side of the political divide ultimately do not work. Yet somone needs to poitn this out, when everyone seems to be going for one extreme or the other.
Still, the stereotype of "real" NT's, is often that they are totally "impassive", no matter what.