[msla]

The counter-counterargument is that we can legalize difficult-to-police but high-volume "sin" crimes, such as drug use and prostitution, regulate them to the point it's impossible to be a criminal syndicate in those realms, and leave the syndicates with lower-volume crimes, such as murder for hire.

Sure, we can't possibly legalize murder for hire and still have a functional society, but how much profit can you really make filling those kinds of contracts, especially in a world with no illegal drug trade and no human trafficking because hookers are now clean and legal? They can try to expand side businesses all they want, but some of them have a natural cap to how much demand there can be.