Can anyone answer why Poker Player is such aggressive to me?
That's something not many can answer. Maybe only PP...
It may be you've done (willingly or not, in that nefarious business or not, I can't tell) something that either offended him badly, either spoiled some business for him or somebody he knows.
Or it may be just a bad impression he got on you, which got worse with that mistake from last year and then also because of his "initial" view on you and the fact you didn't stop engaging into businesses involving money. Plus, if we're brutally honest, your next business idea had its own communication and misinterpretation related issues, which, because of misunderstanding the reasons, was for him another proof he is doing the right thing (I don't think I could've done it much different or better, don't take me wrong, I'm just stating the perceived result).
Then, the fact so many people still consider you trustworthy may be angering him even more. ...Or not; he may be even doing it for some odd sense of fun (who knows?).
However, these are wild guesses. I can't tell what's going on PP mind, only he can. Human mind is... complicated...
As said, grow a thicker skin, you have no other choice for it. From what I know aggressiveness and (cyber) bullying are not against the rules.
but he is picking up my clients and telling them not to hire me because he thinks I will scam them. Do you think this is acceptable behavior?
This is unfortunate and can get him easily from distrust to negative tag.
Just you have to properly and publicly
prove / document this, else it's just your word against his and that pretty much means nothing for a more or less impartial viewer.
Life is too short to waste it on negativity.
That's correct. But since Royse777 has paid some consistent amounts of money from his pocket to handle the mishap from last year, I expect he wants to recover that by working for it. And PP negativity has the potential to harm. If it would not be that, Royse777 could just go on, but as it is ... it can be a problem. And most probably PP knows this and may be also doing it on purpose.