Sometimes for Fe-Ti, a fresh set of eyes on a situation will result in asking certain questions that we didn't consider or sometimes it points out places where we make assumptions that something is obvious and therefore can figure out what information that's important the third party in question may be missing to resolve a situation. Also because Fe tends to check it's reactions with others, even if it comes off as us saying something conclusive, we really are looking to see how other people react when we tell them something. From there, it helps us decide whether we are being reasonable or not. When the reaction seems dismissive, but the person has not asked any questions to clarify, we take it as one of these possibilities
1) Our problems seem insignificant to the person we are telling them to and they are trivializing something that is causing us deep pain (especially if we don't easily talk about unresolved stuff in the first place)
2) They think we are being whiny and therefore not worthy of time or thought being put into what is going on.
3) They don't care as much as we thought they did, or suddenly the balance of our willingness to listen and care seems out of proportion with theirs.
4) They don't feel that we have made enough "deposits" in the relationship to warrant the "withdrawal" of being negativity. We are too much for them.
5) They have misunderstood who we are 99% of the time and are basing their reactions off of this one time when we can't hold things together. What's more they are not even interested in hearing "our side" of things to see why we would behave so uncharacteristically.
I'm not saying that this is all reasonable, but I think it helps to explain why you end up getting such a surprisingly emotional reaction from Fe-Ti when all you were doing was trying to be supportive.
I've found that I cannot make negative emotions disappear until I have either tempered them with other emotions or with context that puts the situation/behaviour in perspective or until I have processed what happened, what my part was in it, what I can do about it now, how I will prevent that from ever happening quite that way again. That requires a lot of narrowing down, considering things from several points of view, looking for patterns, and extrapolating future possibilities. Sometimes you want someone to bounce those things off of or get a second opinion.
To a much lesser extent, I think people tend to do this kind of thing in small real life decisions. Kind of like deciding how much of something to buy and asking a friend, "What do you think? Should 3 of these do the trick?" If they aren't even interested in what you need the stuff for or why you would have any doubts about how much to get, it might just seem to them like you are neurotic, indecisive or they don't really care what you have in your pantry one way or the other. Usually they'll discuss those details and then either agree or say, "But what about this?" They may suggest another product, or they might think of circumstances that would change your decision about how much of something to get. To me, it's kind of the same thing here, just on a bigger scale. If someone said, "Well, do what you want", it just isn't helpful, nor is them deciding that 4 is the magic number, without knowing what you need the product for.