Not obeying the Geneva convention is a double edged sword, it hurts the perpetrators just as much as it does the afflicted. Israel is held to a higher moral standards than other nations, and that is the way it should be. That is why the accidental death of some 20 Palestinians in a major battle in Jennin creates a thousand times more headlines than the murder of 20,000 of defenseless Syrian civilians by its own government. Once a nation goes the slippery slope of dehumanizations of others, the dehumanization of its own is not far behind. This truth is hammered hard in every Israeli soldiers as soon as they join the IDF, and thus the emphasis on the oath of "untainted weapons".
Zeev