Some 4th-grader bible-home-schooled dropout spewed, "Why aren't you arguing to kill off the animals that are responsible for the HIV virus?" 

(Note my kindness on assuming it reached a 4th-grader's level of bible-home-schooling.)

For the very same reason that we don't kill all the Komodo Dragons that might have killed someone from all the virulent diseases in their saliva -- they're native species. Your house-cats are a man-made species and have no native habitat anywhere on the whole planet. Just be glad that we've allowed you to have them -- up til now.

When it comes to trolls (the absolute worst of which are resident-trolls on any forum) there is never a phrase that is ever more true for them, "it is better to remain silent and be thought a fool than to talk and remove all doubt.”

The problem lies in trolls also being morons. The layman's definition of "moron": Someone who is too stupid to even realize they are that stupid so they just keep proving it to the world.