The Chofetz Chaim says in halacha 11 that the extent of not accepting lashon hara is that you can’t hate them in your heart even if you hear one witness testify in court. That can only enforce a vow in court but no one can believe the claim against someone even in court. Certainly, to no pay up any obligation because of the rumors you heard is absolutely forbidden, for example if there are rumors that a bodyguard for an important person stole thousands of dollars that does not mean he should stop getting a salary. He must be paid until an investigation proves he’s guilty. It doesn’t make a difference how small or big of a sin the rumors speak about whether it’s incest, murder or anything else, you can only be concerned and investigate to seek out the truth while taking proper defensive action but you can’t hold anything in your heart against the person. The Chofetz Chaim in a footnote point out a prevalent problem that occurred in his day and might even continue even today where there are people in the community who are known to be poor and are supported by tzedaka. If someone spreads rumors that they are really doing this as an act just to shnoor from others but they don’t really need the money that does not mean anyone can just give less them what they normally give until it’s proven that the allegations are correct. Until then he has an assumption of being poor and just as we don’t require any stranger who asks for money to prove he needs it so to this person who we assumed until now need financial help should not be denied just based on rumors.
The Chofetz Chaim concludes the 6th chapter in halacha 12 by saying that if anyone did accept lashon hara as truth then he must put in all his effort to change his mind and once he does that then it’s as if he never sinned, just as when a thief returns what he stole it’s as if he didn’t steal. Of course he must admit his wrong doing, video, and accept upon himself to never do it again like any other sin that require the proper repentance process. This is all that has to be done if he just accepted what he hears and didn’t tell anyone but if he told others then he must either ask forgiveness from whom he spoke about or (which might be a better choice, according to Rav Yisrael Salanter in order to not make the person feel bad when he finds out lashon hara was spoken about him) he should convince those he spoke to that what he said was false.