mmm... however, i can see how sometimes an INTj would resort to manipulation.
while it is true that INTjs are painstakingly accurate (i catch myself from saying 'never' or 'always' - replace them with 'usually', 'most' etc.

) when they want to get a message across, there are some situations where some INTjs may turn to manipulation. could be, that he/she thinks that an immensely important outcome needs to take place, and it
cannot happen without some manipulation of people involved. it would be unpalatable, but it will be done. especially if the INTjs thinks it can be done with a high probability of success. and it will be done well, to a strategy thought out beforehand, with likelihoods of success predicted for the various possible scenarios.
for example, there are times when i know how saying something in a slightly different way, or omitting something, etc. could cause a specifically different reaction in someone than if i were to say it exactly as it is. especially with people i know well. it's possible that there is a situation where i would judge it better for that person, or an external situation, if i were to cause him/her to react in a certain way, and he/she won't react in that way if i take my normal approach of accurate truthfulness.
then i'd have to make an ethical decision - whether the outcome that i need or want is so important as to warrant risking/spending some of my credibility and bending a key trait in myself. and whether this would signal a serious inconsistency in myself. etc. if i decide to give up some of my precious integrity for that something, then what i'd be doing is manipulation.
incidentally, when INTjs manipulate, it is probably intentional and consciously done, as opposed to other types who may not realise they're doing it.