In most cases, the suffering caused by the harvesting can balance out or outweigh the good done to the transplantee because the unsanitary conditions can cause horrific infections in the victim, not to mention the potential loss of function due to lacking the organ. Also, that stolen organ will likely go on the black market and be sold to a rich person, increasing overall suffering by extending their life and thus their exploitation of the working class. Even from a utilitarian standpoint, voluntary organ donation is clearly preferable, and organ harvesting is just as bad as it is in other philosophical frameworks. Absurdly simplistic analyses like this are nothing but a strawman.