That arguments even worse, it takes it from "killing the kids solves a current problem" to "killing the kids may solve possible future problems", and if that's the standard, then it's never not justified killing kids, as you can always posit some possible future where some kid is going to cause issues.
Say what you will about the CPC but at least they correctly realized that Pu-Yi didn't need to eat a bullet to head off any issues, and that was even after he collaborated with the Japanese.