Not that I approve, but genocide of the Woodlands Indians solved a lot of problems for the early US government. It opened up Ohio for settlement and helped the state govt's concerning land warrants issued for service in the Revolutionary War.
A good point, and, as is always true regarding genocide, unsettling. In cases where a population can be completely annihilated, perhaps genocide can be committed with impunity. That may be how it was with the Woodlands Indians, as well as many other peoples wiped out by colonization and countless wars throughout history and around the world, but there still seems to be a lingering cost for those who would commit this crime and for their decendants. Intangible, maybe, but a diminishment nonetheless. Anyone who commits a crime like this deteriorates morally, with the consequences that brings.
In the case of a proposed extermination the Muslim world, I still find it unlikely that a program of genocide is either practical to execute or capable of making the world safer.
Imal