NATO AIR said:
mj, the problem with that line of thinking is that people usually use it to justify bad deeds
"its normally not okay to cheat on my spouse, but in this occasion,(insert excuse/situation here)"
"genocide is normally terrible, but in this case (insert excuse/situation here)"
"murder is wrong, but in this case (insert excuse/situation here)"
I agree that many people take the idea to places unintended and unreasonable.
The examples you give are good examples. However, it seems each one may be validated with a proper quality.
It seems to me it is a matter of which sphere one is operating.
Your first example: One must first accept the notion that it is always wrong to cheat on a spouse. Are there no circumstances where it would be reasonable to? The answer is no if you agree with the proposition that it is never reasonable to cheat on one's spouse but that is in some way circular. What if one gets married under pressure from the parents and there is no love? And one spouse finds another where love exists? Will we deny the exercise of love to uphold a proposition that it is always unreasonable to cheat? I agree that many people use excuses that are not reasonable. However, I cannot believe that that means that there are no excuses that are reasonable.
I do not hold in respect those who use the idea which I believe in for reasons unintended by the idea. It seems to be an error of a particular human and not the the idea of situational ethics.
Second example: Genocide has within its definition something, in my opinion, that would not create many instances where it would be permitted. However, what about the mass killing of a group of people who only believe that they should kill the rest of humanity and can not be stopped unless by force. It is an extreme example but one that shows that it is possible for genocide to be reasonable. Again, however, that is not the case with most instances of genocide and those who attempt to use situational ethics to justify their actions do not do so honestly.
Third Example: This one, to me, is quite easy to understand. It seems that "murder" implies a wrongful killing. In that case, murder can never be justified with situational ethics. If one was to say that a "murder" was committed within reason it would seem they would be attacking the very idea that the death was wrongful. But yes, I agree that murder is never justified because the definition of murder seems to imply an element of unjustifiability.
It seems to me that the error is with the application of the rule and not the rule itself.
I can't help being reminded of Javert from Les Mis who holds to the principles of his sphere to the neglect of the countless other spheres within life.