Three observations:
1. "Everyone cheats at online chess, including me. The only ones that don't cheat online are liars." Both of these comments are false, as anyone who hasn't cheated online, including me, knows with complete certainty. Your admission that you're a cheater, and that everyone else is also a cheater, simply undermines your own credibility and reveals something quite significant about your own psychological norms.
2. There's a tremendous amount of evidence that Niemann has cheated "in person," including his history of cheating online, his lies about his cheating history, and his ratings history. Moreover, this evidence would surely be determined to be legally "relevant" (in the sense that it affects the probability of one of more elements of the claim) and admissible under Rule 401 of the Federal Rules of Evidence and the overwhelming majority of state rules of evidence, as well as the evidentiary rules of many other jurisdictions. Whether the evidence revealed thus far would be considered sufficient, as a matter of law, to support a finding or conclusion of "cheating in person" is a more difficult and interesting issue.
3. You keep bringing up the case of someone named Ashley Paulson. I have no idea who that is.