I could almost understand the cruelty to the rodent. After all many people just plain HATE mice & rats & so wouldn't really care, just like I don't feel terribly cruel for killing mosquitoes or fleas, and apparently people who feed crickets to their lizards don't seem to have a problem with it.
What I can't understand is if we care about our snakes (and presumably we do or we woudn't own them) why take the risk of having them severely bitten by live rodents? I saw, somewhere, some REALLY GRUESOME pictures of what rodents can do to snakes & I never want to have that happen to MY snakes. I could see someone making an argument for raising their own feeders & feeding p/k to get the most nutrition. I knew someone once who subscribed to that theory & had a burm. Yum, freshly killed bunny! But the rabbit was DEAD when it went into the burm's enclosure, because my acquaintance, although a little odd, was NOT taking any chances of the burm being injured by the rabbits.
So for me it all comes down to the wellbeing of the animal I have chosen to take responsbility for, and f/t does it for my snakes because it is best for their wellbeing.