The article is about actual conversations, not HN threads. Real life interactions have to do with whether the other party perceives you're being a patronizing git, not whether you believe you have something educational to say.

Little Edit: if you think describing 'I don't agree with you' as an 'altruistic desire to educate' and single-handedly preserving the 'validity of discourse' and the 'truth and correctness of human understanding of the world' is anything short of absurdly presumptuous, you might want to re-read the linked article very carefully.