I still don’t get it (although I’m considered intelligent).
Someone says he/she belongs to a certain family, which could be either true or false. Next thing the person is contacted by YW to prove who he/she is. The person doesn’t like the interrogation and becomes abusive in the private email exchange. Your conclusion: “The person is a fraud”.
I see it as follows:
If he/she is a Kletzky, it’s called revealing personal info (no harm was done)
If he/she is not a Kletzky, it’s called lying (which harm was done?)
Abusive emailing makes a person a chutzpenyak, so what?
Where is the fraud???