There is a terrible habit that people have that they feel the need to know what other people did to them or said about them and if they ask and the person refuses to tell them he badgers the guys until he divulges the information. This is certainly rechilus if there is no purpose to knowing, meaning there is no threat against him and even there is potential threat we learned you can’t believe what you here, only take precautions. There are many prohibitions that could be transgressed and mitzvos not fulfilled if one is not careful in this matter. Also, one has to be very careful not to jump to the conclusion all the time that there might be threat against him and he is allowed to listen and inquire about what someone did or said about him. There is a fine line between being cautious and sensing a hunch of a threat and constantly overreacting and that line must be balanced.
The way to find that balance is to be adherent to the positive mitzvah of “with righteousness you shall judge your nation,” which includes judging your fellow favorably. Now this doesn’t only apply to someone who most probably meant you know harm, but the Chofetz Chaim says that if the Torah went out of the way to make a mitzvah for this it must unexclusive, or rather inclusive of many situations including especially if it would seem the person was trying to be malicious, still there is a mitzvah to judge him or her favorably until it is apparent with clear proof and no other choice that he or she is guilty. But if you just know what you heard was true, ley say you even can confirm it on video, still there is a mitzvah to judge favorably, that maybe something was overlooked which could change the whole story. Even if the story could go 50/50 either according to what you heard who are you to make the judgment that what you heard can go either way, if the All-Knowing Hashem makes a mitzvah to judge favorably why should you decide well
that’s only someone who might deserve to be judged favorably but under the circumstances that in my mind this person doesn’t deserve to be judged favorably, how does one have a right to just make that decision, maybe it wasn’t as bad as it it’s made out to be?! Why pick a fight and blow out if proportion a situation that does not have to be blown out of proportion? Therefore, it must the mitzvah if judging favorably even applies in situations where it can go 50/50 either or even if it looks worse than good. It’s not just a nice thing to judge favorably it’s a Torah obligation until it is unequivocally clear what happened.
Now if one has committed the sin of accepting rechilus the way to repent is to first remove from your heart the belief that what you heard is true. If that is hard to do, then just convince yourself that you are missing a part of the story. Maybe something was taken out or was added or the way it was said came out more negative than it really is, including the way his voice sounded might have changed the story if it was said over in a different tone of voice and he skipped up saying it. You should also accept upon yourself in the future to not ever accept lashon hara or rechilus about any Jew again, and say vidui, meaning admit to your sin. This will fix the sin transgressed as long as you have not spread what you heard to anyone else, which is a different story, not impossible to fix, because teshuva is always possible but not for this discussion right now.