"Two wrongs don't make a right"

[Clutch Munny]

Originally Posted by California Tanker

I think your argument is correct in the individual sense, but less so in the collective sense.

You have hit the nail on the head with the concept of perception. Someone who believes that the second act is not, in fact, wrong, will not be affected by the 'TWMAR' comment, and may not see it apply to them. The question becomes one of a larger scale: Joe Homie over there may not see anything wrong with shooting Smitty for dissing his girl, but collective society as a whole does.

In which case, already believing that the shooting is wrong all things considered, they are unilluminated by being told that two wrongs don't make a right.

Sometimes the divider between what's right and what's wrong is pretty clear-cut, sometimes less so. The clearer the case, the more applicable the TWMAR comment is.
NTM

How so? The clearer the case, the less information is conveyed by TWDMAR. The cases seem to resolve into accurately describing the hearer's attitudes, and hence being redundant; and misdescribing the hearer's attitudes, and hence being irrelevant.

[California Tanker]

Originally Posted by Clutch Munny

In which case, already believing that the shooting is wrong all things considered, they are unilluminated by being told that two wrongs don't make a right.

In the case of Joe Homie, he may not already believe that the shooting is wrong, in which case the statement would still provide notification to Joe that perhaps his point of view is one which is in the collective minority. This is also applicable in the case of emotional effect: If someone is feeling particularly hot-headed at that particular moment and time, the phrase could be used in a similar manner to "Hang on a second, sit back and have a think about what you're thinking of doing."

NTM