That's fine, as far as it goes. However, the movie made a point of establishing Superman's code against killing when he confronted Batman. We should have seen Superman confront his internal conflict when faced with a global threat that couldn't be overcome through non-lethal means. We were cheated out of that.
I'm fine with the parademon killing. Soldiers kill, police officers kill and I would too if I were in a life or death situation or the fate of the planet was at stake.
"One can only adore the internet and the opportunity it has proffered to that unignorable segment of the vox populi that
has the acumen of a breath mint but until the web, was blissfully denied a global voice." - Harlan Ellison, July 23, 2013