I don't think ignoring the guy who committed genocide simply out of a petty desire to avoid giving him what he wants would've been very proper, especially when there's no indication he wouldn't have tried to "motivate" us again in the future.

If you choose to believe that he only ended up with a realization of how utterly empty and pointless his life had been in the end, I'd honestly consider that the best kind of poetic justice he could've received.