Another comment explained it pretty nicely:

But you can’t have [a platform with absolute free speech] while allowing for hate speech either because hate speech silences the voices of its target.

It’s basically the tolerance paradox but with free speech.

The owners and operators of the platform.

In general it’s the wider community that decides all that.

There are consequences in holding and sharing views that are disagreeable with the community in which people share them.

People are free to air those thoughts, but others are also free in shunning them for those thoughts.