What? INTJs don't lie any less than any other type. They're not that emotionally aware and are thrown off by the more complex, emotionally charged language that I am fascinated by and find revelatory.
They aren't honed or elegant emotionally because their 'tasks' aren't in the arena of profoundly understanding other human beings. So they choose to use this sort of black and white, direct, directive, chunky language because it's functional for them. And they convince themselves that only the emotions that they give merit to are worth giving merit to. A lot of what INTJs perceive as 'lies' are actually just complex truths that fly straight over their heads.
They convince themselves that their bluntness is from honesty, but it's not...they just don't have enough emotional nuance to operate under situations that are highly emotionally complicated. Maybe they just convince themselves that it stems from 'honesty' to make themselves feel better, maybe it's because they genuinely cannot comprehend that other people have vastly different (and equally or more legitimate and worthwhile motives) than them.
I've SEEN INTJs LIE. They lie when their careers are in jeopardy or when they are on the brink of a big accomplishment. They start shutting down information about themselves that they don't want to know so that they can preserve the image of themselves that they want and get to goal X.
What one type might consider a lie, another type might consider a crucially necessary invasion for their 'task.' What one type might consider 'honesty,' another type might consider un-evolved, primitive bluntness for the sake of self-preservation and not for the benefit of others. IT'S ALL RELATIVE.