It's pretty common on the Internet and on HN too, and in public debate. Aggressive, confident assertions deny others the power to disagree.
Contempt and shame - super-popular rhetoric these days - achieve the same thing, and they are related (both kinds of rhetoric are an aggressive display of arrogance). They assert, implicitly, that there's no way to debate this person.
Anger is another similar tactic.
Then if you don't understand that it's tactical, you give up. So far, to my amazement, very few people seem to understand it; almost all take it at face value.
Contempt and shame - super-popular rhetoric these days - achieve the same thing, and they are related (both kinds of rhetoric are an aggressive display of arrogance). They assert, implicitly, that there's no way to debate this person.
Anger is another similar tactic.
Then if you don't understand that it's tactical, you give up. So far, to my amazement, very few people seem to understand it; almost all take it at face value.