Correct, you aren't obligated to explain anything to anyone. If you want your opinion/idea/statements to be taken seriously however, you have to back them up and can't just speak absolutes into a void.
I disagree on your conclusion. I think there are certain ways of explaining your point of view amongst an ambiguous crowd.
Monologues can easily be boring. They are hard to put together for most people and you have to have implied consent from the crowd to be monologued. People don't like to be forced to be polite to listen to anyone for more than 30 seconds.
But there are certain ways of conversing where you have time to explore deeper. Unfortunately, not everyone is open to conversation for the sake of argument.
I think you and the person you're replying to just have different ideas of what you mean by "people". I think they'd be right in saying you can't speak absolutes and get away with it in a group of curious and non-impressionable people who will challenge what you have to say and will try to understand your POV too, but you're also right in saying there's groups of people where the same strategy will backfire.
It is true, just incomplete. Preaching to the converted doesn't require this evidence and argument, but _in general_ you need that capability. If you want popularity you have to customize your pitch to the audience.
You know who treats Internet discourse as a good way to teach and learn? QAnon.
If your systems can’t prevent you from falling for QAnon, flat eartherism, or the time cube, you are exploitable and are likely already actively exploited.
Believing what you read in an HN comment is a terrible idea.
In fact, explaining things is often a great way to lose credibility to large swaths of people, as you'll have become boring and confusing.