I czan't explain how the people you described behaved toward you and around you. That is how people behave sometimes. I stay away from chat because of the immaturity level and because it seems some lurk there just to abuse others implicit trust in them. I'm sorry for you to be still struggling with this aspect of life. The fact is while these things affect you negatively, the normal path of development to deal with these situations is that one becomes assertive when one recognizes the issue arising for them. Even if the assertion is ineffective one will feel better for trying. There is also boundaries, being sympathetic isn't the same as feeling as if it is happening to you. The first is normal the second isn't.
Asserting oneself may look like letting someone know they have just hurt your feelings, telling them what they have said is out of line or insensitive, etc. (I admire that you know that quickly how something affects you)
Being sensitive to every person's personal needs is not something society as a whole can do. It would not be able to function if it tried. That is why we learn to assert ourselves. The penalty for not learning to stand up for oneself is to feel discounted, insecure and hurt quite often. Even when one is not successful after asserting oneself one feels good that one did assert themself.
There is besides the benefit of feeling good almost immediatley when one stands up for oneself or one's belief the fact that you may be teaching another something they are not aware of or didn't even consider might be an effect of their behavior. This too can make you feel good and help someone.
It isn't the success or failure of standing up that has the benefit, it is simply the standing up to be counted that gives the benefit. Success, if it occurs, is just icing.
Otherwise I'm not sure what you might do in these situations.
As Mark Twain once quipped, history may not repeat itself, but it does rhyme.