A line from a Neil Diamond song that has stuck with me through the years is "gettin lost is worth the comin home". Not exactly the same as "the end justifies the means", but it reminded me of it. Your question is about "the end does NOT justify the means" which is different from how I've heard that phrase.
I sort of like the Neil Diamond line better, because it's about looking for the good in everything, where as justifying the means is more about having a ready excuse for an otherwise inapproprite action.
I think in either case its a value judgment, and therefore unprovable, either that the end does, or does not, justify the means. Sometimes the "it does" saying fits, like in the case of the pain of childbirth. Sometimes the "does NOT" version fits, like "sure, I abused him, but he turned out alright". Therefore I think neither form is always consistently correct.
