Well, sometimes thought-experiments are dirty tricks and merit having their premises dismissed.

"If X, Y, and Z were all true, wouldn't that mean we should kill all the coders?"
"Well, hypothetically, but none of X, Y, and Z are true."
"Aha! So you concede that there are certain circumstances under which we should kill all the coders!"

My preferred answer being:

"I can't occupy the epistemic state that you suggest — namely, knowing that X, Y, and Z are true with sufficient confidence to kill all the coders. If I ended up believing X, Y, and Z, it's more likely that I'd hallucinated the evidence or been fooled than that killing all the coders is actually a good idea. Therefore, regardless of whether X, Y, and Z seem true to me, I can't conclude that we should kill all the coders."

But that's a lot more subtle than the thought-experiment, and probably constitutes fucking tedious in a lot of social contexts. The simplified version "But killing is wrong, and we shouldn't do wrong things!" is alas not terribly convincing to people who don't agree with the premise already.