Many people like to discuss ideas they may not believe (or even like!), in an effort to understand them, and the people promoting them. This "discourse" used to be considered a pleasant passtime at worst, and at best an educational pursuit that might raise the common condition of humanity to a higher state.

This is an old tactic used, historically by religious cults to separate potential members from their soon-to-be former lives.

Because they've become sociopathic.