There is a very strange dichotomy on how to approach lashon hara if heard and could be useful. The Chofetz Chaim says though it’s forbidden to accept lashon hara according to the Torah it is permitted or even obligatory to be cautious for what you heard in order to protect yourself or others from possible harm but at the same time you also must believe in your heart that this person is no different than any other Jew and has a chezkas kashrus, he an upstanding good Jew even though someone said something bad about him. This has major ramifications in halacha for example, if someone says that he saw someone eating non-kosher out of spite, meaning he had two steaks in front of him, for example, one kosher and one non-kosher and he put aside the kosher and ate the non-kosher one that shows he doesn’t care about Hashem’s mitzvos as opposed to someone who’s a glutton and just likes non-kosher food because it tastes good. Now if there were two witnesses that testified in court that this person sinned to spite Hashem not just because he liked eating non-kosher food and the court makes a decision and declared that this is Jew is outside of “your nation” then though he is a Jew still but there are certain laws that don’t pertain to him, for example if he lost an object you found you don’t have to return it to him, if he asks for tzedaka you don’t have to give him, or even if he is captured you do have to redeem him. But this status only applies if it was declared in court, but if you just hear someone tell this story and it was never taken to court then the person must still be treated as a normal Jew all halacha applying to him. This is true even if he is known to be on the fringe and was known to do other songs but not bad enough to be out of ” your nation” you still can’t believe the story and treat him differently though you could take note of any concerns and take precautions if you think this person can harm you or others.