In non-life-or-death situations, people endure quite a large amount of discomfort to achieve other goals. But a high-enough level of discomfort kills people. Does this mean the ones enduring small amounts are irrational?

Reducto-ad-absurdum is a proof only when it takes into account everything in the argument. In life-or-death examples, other normally-included portions are dropped, making the argument something else entirely. It's just a straw-man attempt, not a valid point.

It's not a straw-man. I have attempted to refute nothing. I was merely asking my parent to consider how he might behave in such a situation.

I used a different situation, it is true, but only because I have found being on the instructional end of cheating feels very different than you might imagine, so I guessed my parent was not familiar with it.

You attempted to refute the claim that people should control themselves better in such situations. And you did so very clearly, by inferring that spreading the mood to the 75% was perfectly logical.

As a student who has not cheated, but has had to sit through countless lectures about cheating, and a few where large portions of the class did, I ask you and (other?) teachers this question: to whom are you teaching? The ones who are learning, or the ones who are cheating?

I understand that you're stuck with both, but either find motivation in the successes or consider another line of work - it's part of the job. Otherwise you're screwing the ones who did the right thing.

He's not saying it's logical. He's saying it's inevitable based on how people are wired.

And therefore we shouldn't control ourselves better?

People have limits. I don't know enough about the situation to know if he was under the kind of load that would cause most people to act differently, but I suspect that is the case.

No one wants to kill anyone here.

I am all for using analogies to reassess my views, but the degree of comparison should be similar for the analogy to work. I can't even process for a second how cheating is anything like threatening to kill someone.