I might come under fire here - and I realize at this point in time we have no way of determining if the murder request was real or forged by authorities - but, assuming it is indeed real, I understand what DPR did and why he did it.
I share the opinion that the government has no right to prohibit consenting adults from engaging in a peaceful transaction - the drug trades that SR enabled. It is undeniably true that, should a buyer or seller be caught by Law Enforcement (LE), they would be subject to strict punishment - locked up in a cage, often in extremely unsafe prisons, have their life ruined, and in some jurisdictions even be subject to murder capital punishment.
DPR knew this, and the blackmailer knew this. The blackmailer knew that, if he followed through, he would be subjecting thousands of peaceful individuals who did nothing wrong to prosecution and persecution by LE. The blackmailer knew very well that thousands of peaceful members of SR would be locked up and have their lives ruined.
Consider an analogy: if someone went up to Oskar Schindler and said "I know you are helping Jews escape; if you don't pay me $150k I will tell the Nazis about it", don't you think Schindler had the right to prevent that person from making that known - even if the only way to do so was murder?