I actually think I'd put a lot of INTP's I know above the ISTJ's I know in a list of most close-minded and rigid people I've met. After all, they're so much smarter than everyone else aren't they, so surely whatever they say is bound to be more right than anything we humble mortals can say or think?
I mean, I've seen INTP's on here argue very close-minded attitudes against for example, homosexuality, transsexualism etc., whilst my mother the straight-laced ESFJ will join her colleague on a gay pride march without blinking an eye. And the ISTJ I know almost always apologises and admits his faults if you point out that he's been rude or insensitive, whereas many INTP's will argue to the death that they shouldn't HAVE to be sensitive and that social conventions are stupid so it's your problem if you saw their behaviour as rude, and that their rudeness was only in your mind etc etc... yawn!!
Maybe it's because I've spent a lot of my life around J's, with mostly positive results, that I don't share this 'P' prejudice against J's.