That's not how for example newspapers work. They will publish opinion pieces from people and with opinions that they themselves strongly disagree with, because they see it as their duty to promote freedom of speech and a healthy public debate.
Or parliament debates, where representatives for smaller parties get to have their say on equal terms as the big dogs.
Some countries even force radio and TV stations to air a certain amount of time to each candidate for their propaganda before an election (which can be hundreds of people).
I'm happy to say that even HN largely doesn't work like that: many of us upvote comments with which we disagree because they are well thought-out or interesting, and made us reconsider our viewpoints, even if we ultimately settled on the same viewpoint as before.
Or at minimum we don't downvote as knee-jerk psychological defense mechanism.
And Dang doesn't go around removing comments and commenters he philosophically disagrees with either, even when they're obviously wrong or hyper-emotional, so long as they're not hurting the community.
I think the ability to block/ignore users would be much better than having down votes. If some poster is simply insufferable to a person, better that they have the ability to block than that they silence by downvoting.
And upvoting people you disagree with if they move the discussion forward in a good way is something we all should do, but it is a struggle.
Or parliament debates, where representatives for smaller parties get to have their say on equal terms as the big dogs.
Some countries even force radio and TV stations to air a certain amount of time to each candidate for their propaganda before an election (which can be hundreds of people).