You can have multiple spaces in a community. Some for discussion, some not for discussion. You can also have different communities, some that allow discussion and some that don’t. To expand on the house analogy, if someone walked into a Star Wars themed bar with a shirt reading “Star Trek is the superior sci-fi show” and people got mad and tried to force the Star Trek to leave, they would be justified. That example is overly dramatic, but there are spaces online and offline where people want to enjoy or discuss a thing and should not have to be subjected to people who disagree with them. If some wants discussion, they can create a new space and advertise that space as friendly and open to discussion.

This post is a perfect example of being a space open to discussion. The OP wanted discussion and so people come in with that mindset. But if the OP said “What’s everyone favorite fruit?” and someone commented saying “I hate fruit”, that comment would not be appropriate for the post. It would be off topic and inflammatory and likely be cleaned up (removed) by a moderator. I know people believe that moderators can overreach, but those spaces belong to the moderators. If you don’t like how they police a community, find or make a new community.