I'm going to post my two cents before reading any answers, because I always find it interesting to compare- and posting first is the best way of knowing what opinion I had before I read others. Basically, this is a disclaimer for if I happen to repeat what already been said.
Question: How do you know you are right?
In regard to incidents which evoke some kind of emotional charge in me: while I'm aware that sometimes my tone- which can get emphatic if there's a strong emotional charge involved- might inadvertently indicate certainty, I only actually ever feel like I know something if it still appears to be true after the emotional charge has faded. As long as there's still any emotional charge though, I'll have doubt, because there is a tendency in people (which I'm no exception to) to ameliorate unpleasant emotion with a narrative that externalizes blame/shame. Even where the unpleasant emotion
is indeed because someone else has crossing some kind of line, in regard to power dynamics between people- it's only after the emotional charge has passed that I'll get any solid feeling of knowing.
Ultimately, 'knowing' is just a feeling- it isn't a black-and-white, "either I
know or I
don't" kind of thing- and I feel it inversely proportionate to the kind of emotional charge that would otherwise drive any kind of narrative. The less
attachment I feel to a suspicion being 'true', the more I can trust that it is. (And less attachment to it being true means it's that much more open to change with new different information.)
Like how do you know that Susan secretly hates Barbra? How do you know whether someone has bad intention? Are you able to catch when you are wrong. What is the line between trusting your people intuition (not necessarily mbti intuition), and trusting what someone else says about them self?
At this point in my life (46 years old), on account of getting burned by not trusting my gut (because I couldn't effectively put my reticence into words), I always trust my gut when it tells me a certain situation or interaction with certain people isn't right
for me. I'm more skeptical of the first narratives that come to mind about it (because it's just not possible for one person to see all the possible ends for others), but I've also learned that 'gut' feelings are always there for a reason.
If someone tells me something about themselves (for example, stating what their intentions are) and my 'gut' feeling thinks something doesn't quite add up about it, then it's not available for me to believe them (to take note that my senses are telling me something other than what they're declaring and reserve judgment: yes, but to actively
believe what they're saying in spite of all my own sensibilities: no). I rarely get confrontational, but I'll just kind of catalog the (fleeting) observation that what they're saying doesn't match my own sensibilities. If they are a constant part of my environment, either something will eventually fall into my purview to make sense of why I was mistaken, or enough of these kind of incidents will happen that I'll feel inclined to avoid interaction with them. But I think it's actually unreasonable to state something about ourselves and to
need others to believe it/reflect back affirmation. It's one thing if I've already gotten close to someone, it's kind of already been established (by their behavior as much as by what they say) that honesty is a priority, and- as someone close to them- they need me to remind them of how honest they are (by already having proven it) when they are feeling low. But if someone is trying to establish their character with me by dictating what I should believe about them, and/or (even worse) incessantly explaining to me how my perception is wrong if I don't see them as they want to be seen, I'm going to end up distancing that person as much as I can.
As far as the specifics of 'why'/filling in blanks about 'reading' others- if it's something that bothers me to distraction, which usually means it appears to me there's some distortion of power dynamics going on and either I feel taken for granted or I see someone else getting taken for granted (exploited in some way), then I'll ask the opinion of someone else whose judgment I trust. The possibility that I've asked someone so like-minded that we simply came to the same conclusion because we have the same baggage is always a factor; at the same time, I have had too many experiences of asking people who think differently, getting told it's nothing, and then having it ultimately collapse back in on me, to attempt to ignore a gut feeling altogether. There is ALWAYS a reason for the gut feeling. At any rate, if I have a gut feeling that I should establish some kind of boundary, then I establish it. Another person's opinion, even if they think so much like me that it doesn't make me especially confident of the way we filled in the blanks, will usually at least help me make a more specific boundary; if the boundary has to be completely nonspecific because I didn't have
anyone to bounce the situation off of to get an opinion, then the gut feeling eventually lead me to a total avoidance of the person. In other words, I seek the best external judgment available to bounce my gut feeling off of, and if there isn't one available then I go with the gut feeling and avoid someone/something altogether.
Things that reinforce my feeling of knowing in regard to the 'whys': when someone else bounces reality off me, unsolicited, and states the same 'why' I suspected myself before I even say anything; the extent to which the other person's judgment (whom I am bouncing reality off of) has garnered my respect; and/or the extent to which they think differently than I do, yet I still respect their judgment (iow: if they think differently and see the same 'why', that strengthens the feeling of knowing); and again, more than anything, if the 'why' still appears to be the case after the emotional charge has completely passed.
Also, I don't like the phrase 'bad intentions' because it implies the person is aware their approach to others is exploitative or controlling (or whatever specific way in which someone's approach to interaction is on the dominating side of the power dynamic). Most people who exploit the kindness or naivete (or whatever) of others aren't aware they're doing it- it isn't done
to exploit, per se, it's done to compensate for their own inability to effectively regulate their own emotions and they're typically blind to it. To them, it's just a sort of fuel that everyone gets from interacting with others, as if interaction inherently provides everyone with that kind emotional regulation, oblivious to the fact that they are actually siphoning internal resources off of other people. It isn't 'bad intentions' so much as human frailty.
Why should I believe that you are good at reading people?
I don't think anyone,
ever, should believe another person is good at reading people simply because they say it is true. It's like when someone claims to be self-aware. These kinds of skills are self evident. I mean, it's one thing to say it I guess (though you're doing yourself no favors if it isn't completely 100% true, because other people can tell and you'll be establishing a
lack in self-awareness if your skills don't pass muster), but it's another thing to
need others to believe it because you're saying it. The latter is kinda messed up.
Where another person is applying any kind of coercion/pressure whatsoever to convince another person they are good at reading people- for example, "it's hurtful that you don't believe it," and/or they threaten to sever a connection that otherwise feels good unless they start getting affirmation that it's true, and/or there's any kind of passive aggressive retaliation for not affirming it, or any other type of emotional coercion- I think it's always safe to assume it's more about that person's ego than it is about them actually being good at reading people.
This kind of thing just
is self evident.
because i can read you better then you can 
.
let the other person have the shit.
