IMHO mentioning a rumor you only help spreading it. And again IMHO if you want to defeat a rumor, you shall attack those, who are telling it, discrediting them - this time mentioning that rumor together with their name. Then people will associate it not with “something that could have happened somewhere”, but with “someone saying something”.
Then there are two options. First - they ignore it, consider it your win.
Second - they start arguing, telling it happened. In that case you just demand them to bring proof, since it’s always duty of an accuser to bring evidences - you don’t have to defend anything against rumors, only attack them back.
If they don’t bring the proof - you can just smear them to the wall verbally - whatever they or you say after that, it’s your win.
If they bring proof - if it is not relevant or falsified, show that and again, it’s your win.
If it’s genuine - well, then you’re fragged and it will be time to bring apologies.
Success of the scheme is not guaranteed. Use at your own risk.