Yes, you beat me to it, but in a more humorous way. I was going to say the aliens would not have restrictive rules of engagement for the sake of being fair and out of concern for “world opinion”.
An insurgency against a civilization capable of star travel will last nanoseconds.
Here’s a simple math exercise for you:
Suppose aliens come and want Earth intact but kill off all the troublesome humans. How big a hole would they need for a mass grave big enough to dump every body on Earth into ?