for some percentage of the population, morality isn’t a guardrail

There's more to human behavior than expressing ideas of correct behavior and violent enforcement of those ideas. Both of those are very limited, rely on oversimplified abstractions of how people are, and often have adverse side effects. What we are like and how we live is a complex product of how we engage and relate to our environment and the people around us; the best overall solutions to problems will be holistic improvements to that environment.

To extend your medical analogy, sometimes serious threats to your health call for antibiotics, but it is not the case that scouring your body of foreign organisms will make you healthier in the absence of an antibiotic-treatable threat, it's actually important to have those.

Bringing it back to how online spaces are organized, I think it's important for most people to feel like there is a way to express their genuine thoughts because if it's all just people finding different ways to repeat a dogma, that's a failure of communication, communication is not meaningfully happening, and an environment where you are unable to communicate is a shitty and dysfunctional one. That doesn't mean all spaces must accept all points of view, but sincere and open communication should generally be a priority, protecting that is what free expression is about.