Why are Christian Bookstores Allowed to Ban Books?

Thinking about this in the context of a remark I made in a concurrent thread:

I really do get the “anti-cancel-culture” viewpoint that not much useful purpose is served by an unending vicious cycle of people being mean to each other. Where you say something that I find insulting and then I boycott you for insulting me and then you denounce me for “canceling” you and so on all day long on the merry-go-round. At some point somebody’s got to be willing to break the cycle by just letting it go.

But my point is that you can’t just arbitrarily pick a point in the cycle and say “This is where the meanness has to stop.” Trying to make such rules is just too vulnerable to subjective bias and the influence of existing power structures.

We can certainly make rules about what specific acts of meanness we will or won’t tolerate: e.g., no violence, no threats or intimidation, no doxxing, etc. (and we have to be willing to back that up with official enforcement). But trying to find a place on the cycle that reliably separates permissible “speech” from impermissible “bad cancellation” just doesn’t seem workable to me.