Not all opinions are valid or should enjoy equal treatment under the law. The original framers of the laws knew that and put in limits, and also knew that social mores would change, so recommended that the Constitution be rewritten every 12 years.
For society to work, people have to agree on a base set of ideas and beliefs. That's the social contract. People operating outside that social contract either need to come into line with the community's agreed-upon standards, or separate themselves from the community and establish their own.
There's nothing draconian or unoriginal about this. It's the way societies have been built since the ancient Egyptians.
Tend your garden, or the weeds will grow. You want Facebook to be a place you feel comfortable and the community is vibrant and interactive? Then you need to weed it. Laissez-faire never created community.
See, you have already been conned by the psychotic right wing's redefinition of terminology and principles. It is perfectly reasonable for people to expect others to behave in a civil manner when in the public sphere. The right has reframed this to "all ideas are equally valid", and you are arguing from their far-right side of the psychosis.
Not all ideas are valid. Not all ideas are to be treated equally. That's asinine.