The reasonable reaction to a dubious unsupported claim is immediate out-of-hand dismissal. In asking for a citation, they are giving you the benefit of the doubt; i.e. doing you a favor.
He's one of the most public figures in the world right now, with hours of video "evidence" widely and easily available. Asking someone to prove he did an obvious thing in public is demanding unpaid labor.
This is not the same as expecting someone to back up a claim of a homeopathic treatment for brain cancer.
Then you should easily be able to link to one. Hand-wavy accusations are irrefutable, and it is therefore irresponsible to make them. Once a specific case can be examined, it can be properly debunked and/or debated. But a vague accusation with the source of “everybody knows it” is worthless. Or in other words: Links or it didn’t happen.
He's an asshole, I get it. But half of what is said about him is false (pee pee tapes?) that Americans don't give a darn about what is true.