I have, in the past, intentionally manipulated someone. I did it when my situation was desperate and I believed the relationship was virtually unsalvageable anyway. Also, the other person had made it relatively obvious that they thought I had fluff for brains. And they were correct that they are much more intelligent than me. I'd say they have at least a good twenty IQ points on me. The chinks in the armor were just glaringly obvious to me and I couldn't resist a few subtle pokes. I was actually surprised it worked.
The end results were not all I could have hoped for, but I'm not sure they were worse than if I had not done what I did. I would apologize for it if the person had not before and since made their disdain for me so plain. I should probably feel worse about it than I do, but I do not think I would do the same thing again. It would have to be a pretty crazy situation to make it worth it.
Normally, it's not behavior I engage in. I pretty much have to believe the other peson has already declared war on me in order to make me feel it is in any way justifiable. I've also learned that meddling in general is a bad idea. Especially with Ps. They can moan and wail about their circumstances and how much they hate them, but sometimes when they finally take decisive action, it can be like jumping out of the frying pan and into the fire. I try not to project my need for closure on others anymore because of that.
If I withhold information in normal circumstances it's because I am covering my ass. I usually tell on myself compulsively, but there have been a few occasions when I considered the other person unreasonable or I didn't think it was any of their business.
I will change my communication style to match the situation. But because I'm married to an INTP who has a serious thing for autonomy and has a strong aversion to manipulation, I've had to become more aware of it than I otherwise might have. As a general rule, I dislike people trying to manipulate me and so I try to make a point of not doing it to others. I have a lot of doubts and uncertainty about life, the universe, and everything, but I believe in karma. I'm superstitious and self-interested enough to be worried bad stuff will happen to me if I do bad stuff to others. I try not to dish out more than I think I'd be willing to take.
I care about others in that I find the discomfort of others to be unpleasant to myself. I don't consider it much of a virtue, but rather being a member of a social species. It's kind of hardwired in and involuntary. I do consider people that lack empathy somewhat defective or dysfunctional. I care about my loved ones because, to varying degrees, I consider them extensions of myself.
Sometimes, the reason I avoid the suffering of others is because I don't think I can do anything to make it better and it is useless for me to be miserable when the people that are suffering gain nothing from my misery. It serves no purpose and the feeling of helplessness and anguish is incredibly unpleasant.
The crazy thing for me with this thread is to just what degree my givashit is broken. This stuff used to really bother me. I probably finally grew slightly thicker skin because of learning to cope with my family's disapproval. Eventually the receptors must get worn out or something. Took long enough.