You are confusing rhetoric with dialectic, and wasting your time.
You cannot answer rhetoric with a dialectical opening (show me the evidence) because the rhetoric speaker has no interest in you or dialog with you.
Well duh!
Nonetheless, put it to them. Make it so on-lookers have to, themselves, wonder what examples there are to prove such slander?
Doesn’t matter they don’t answer. That just proves they have nothing.