I take it you dont DM much anymore... right?
Although if they get captured in the future, I could bury them in the same manner... I'd never put them into an unwinnable situation as railroading would just breed resentment and I like to keep things fun.
I DM more or less every week for the last 30 years or so. It is just that perverse torture-hobos would find little enjoyment at my table. Karma, you know, cause and effect, all that. No-one at my table would enjoy a tale about extended and grotesque torture of a defenseless victim.
Out of curiosity; why did they care what was the "least evil" way to deal with him? So they could avoid it? Your players does seem to make Hallibal Lectre seem like silent little lamb with their utter and gruesome evil.