What a ridiculous gaslighting question.

Asking us to prove that cats killing wildlife is a bad thing.

A guy once told me that they remove the fallen logs from the Canadian forests because fallen trees are messy and ruin the forest. How do you even respond to such a stupid concept?

Not entirely, we should be worried about almost all of it but we shouldn't underestimate the reproduction rate of mice and rats that are quite successful in urban areas. If we were to remove all domestic cats we would almost immediately be overrun by hundreds of billions of them and they could quite literally end us. Mice population can double in 3 weeks. If you start with a few hundred million 30 weeks would turn into a few hundred billion and 60 weeks a few hundred trillion (2,4,8,16,32,64,128,256,512,1024) If they are currently killing 30B you might start with 15B mice rather than a few hundred million.