Human beings have tried to create 'rules' around warfare for hundreds, if not thousands of years. And yes those 'rules' had plenty of grey, yer they were often hypocritical, discarded at times, differed from society to society but there was a reason why we tried to create some sort of lines.
The Russian destruction of the damn, targeting of civilians, kidnapping of children are rightly held to be atrocities, because they violate such 'rules'.
Believing that there are lines that should not be crossed even in warfare is not pearl clutching, its having some fucking sense of history and humanity.