On this forum, I've come across many misconceptions about ISTjs, such as how their spirituality is under-developed and how they are overbearing, manipulating dumbfucks. I've also read about how ISTjs supposedly manipulate people, can't understand emotion at all, are back-stabbers, and will resolutely defend even an obviously incorrect conclusion. Expat suggested that they brainwash themselves.
Maybe I'm being a little too touchy here, but I'd just like to correct these misconceptions.
ISTjs can have developed spirituality and under-developed spirituality. But I will mention that there is such a thing as a spiritually-aware ISTj. I'm one of them. I was raised as a Catholic Christian, broke with this faith when I couldn't see the sense in it (in my early teens, which was really quite young to be thinking about spirituality). I'd mention that I was a strong believer in the Catholic faith before I broke with it. Then, I was an atheist for some time, and now I'm a Buddhist.
I believe in Buddhism because science supports it. This is empirical and logical - which is showing itself. But the point is that ISTjs aren't spiritually devoid. I'm a firm believer in Buddhism and support it entirely, embracing all religions.
ISTjs can be overbearing, manipulative dumbfucks. But not all of them are. I belive in manners and politeness not to conceal my manipulation and survive, but because it is the right thing to do. Unnecessary conflict is avoided by politeness. I know someone who is insensitive and socially backwards, who thinks that it's cool to be rude and say "Fuck off" casually. He is bullied because of this attitude. By being polite, his entire quality of life would be improved a hundredfold. Except that he won't listen.
ISTjs can be sensitive and considerate, and polite because of that. It would hurt me too much to bully someone - there would be no negative emotion to fuel me. I'm too self-controlled to get carried away with anger. In fact, one of the only things that'll get me angry is someone bullying me, or being inconsiderate. I think that, like most introverts, I can choose to become aggressive by turning upset into hate and rage. But that side of me has only rarely come out, less than ten times in my entire life.
ISTjs can, therefore understand emotion. They probably don't understand it well, but they do understand it. So, when you are making ridiculous hypotheses about why an ISTj is polite because he can't feel emotion, ask an ISTj for his opinion.
I will agree that ISTjs defend obviously incorrect viewpoints, but the way you talk about this quality makes it seem incredibly negative and bigoted. This isn't true. I don't brainwash myself. If I believe in something, it is because it is a logical and valid viewpoint, NOT because I want to. I defend myself with logic, not being a prick. I can see and empathise with other people's emotions and arguments.
ISTjs can be some of the nicest people that you can meet. Very few people are patient, genuinely polite, and will keep their word.
I apologise for this long post and any anger in it, but I'm somewhat insulted that you assume these things about ISTjs that are in no way representative of ISTjs as a whole. Before making these conclusions, please consult actual ISTjs, and exercise some common sense.