Our Gemara on Amud Beis discusses the prohibition to buy stolen goods. The Rambam (Law of Theft 1:1) warns that to buy stolen goods of any kind is a grave sin, as it encourages the thief’s behavior.  Based on this, Yam Shel Shelomo (58:1) rules that it is still prohibited to purchase from a thief even if he technically acquired the item via making substantial changes so that it is no longer the same object, such as weaving wool into a sweater. After all, even if now it is legally not stolen goods, it is still encouraging sin. However, a responsum of the Rivash (273) rules that once the stolen textile has been changed and crafted into a wholly different item, it is permitted to purchase.

Sefer Daf Al Daf brings down a question from Rav Meir Stern (Commentary on Shulchan Aruch Harav, CM 7, end of Biurim 9): How does the Rivash not consider the Rambam’s ruling, especially when the Rambam’s position is supported by a powerful moral argument about incentivizing sin.  Rav Stern answers that since the thief has to go through all the trouble of refining and crafting the stolen raw material, it is not such an incentive to steal, given all the bother. So to speak, he might as well run a legitimate business for the same effort.

I believe Rav Stern is basing his argument on the psychology of a certain kind of thief. This is an impulsive person, who cannot delay gratification. Why else would he choose a life of crime? Thus, the act of buying material he crafted from stolen goods would not encourage his criminal behavior, as this was not his typical MO and in the future he would stick with more “profitable” forms of larceny.

This only addresses a specific kind of thief, however the white collar criminal or the con artist, seem to enjoy the efforts and machinations to commit their exploit. However, the halacha does not consider whether we are encouraging or discouraging such a person, perhaps due to the thought that he would be crafty regardless, and outwit any efforts to detect his thievery.