Discussions generally don't sway people. When someone has a fixed worldview and you present facts that undermine that worldview, he perceives you as a threat (like he would a large bear) and reacts to those facts with the same fight-or-flight response that threats generally elicit.

Online, this fight-or-flight response manifests as people downvoting you, flagging you, doxxing you, and so on for presenting hard-to-refuse facts and arguments contrary to any entrenched but incorrect narrative.

The problem is exacerbated on HN by high-karma accounts having the ability to flag discussions to death without engagement and essentially end them unilaterally.