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Definitely applies to the given example- Bob's argument bears a little more weight if he's not the one who killed them on land, either (ie, he's just the guy that got rid of the bodies), but either way he's pointing to the fact that he didn't do something worse as a reason he should be rewarded with reduced punishment.
Might be worth mentioning the legal concept of mitigating circumstances
in the description, as it's a case where prizes for basic decency are often requested and sometimes given. Say, Charlie has a heart attack when Dave tries to rob his store, but Dave requests leniency for the fact that he called an ambulance and gave Charlie CPR until they arrived (and then Dave ran away with the cash).
Yep, that one counts. Tropes are flexible.
Does it count as Wants A Medal For Basic Decency if the character doesn't want a reward but less harsh a punishment for not doing something even worse than what he did?
Something like this: