Having a slur filter on a particular forum instance designed and chosen by the admins of that site is a perfectly good idea. They know the character of their forum, they can choose what is and is not appropriate to say.

I think it does display a narrow-minded agenda for the authors of hosting software intended to potentially host a wide variety of forums to declare unilaterally that all sites hosted using their software must use a particular slur filter declared by them, or else create and maintain a fork.