Broadly speaking, it is not illegal to demand (or ask for) money that you are duly owed. TMAN might have violated debt collection laws in his posts depending on where both he and BetKing are located, and other factors; if this is the case, I would consider it to be a process crime.

I don't condone how TMAN went about trying to collect the debt he purchased, and above all I think it was immature and intended to create drama, but I don't think it would meet the legal threshold of being blackmail or extortion.

Elsewhere in the thread you are quoting, TMAN had purchased alleged debt owed by the person he was asking to pay. Even if the debt was invalid, I believe in this case that TMAN believed in good faith the debt to be valid, and BetKing did not dispute the debt to TMAN prior to TMAN making any of those statements.