You either need to ban /r/TheDonald, or just accept it for what it is, hold your nose, and walk away. I believe that I'd choose the former, but if I had the power to do so I might feel differently.
But this is the worst possible thing. It makes Spez look horrible, it undermines trust in the site and the admins, it confirms all the nutty things the alt-right believes about Reddit, etc. It makes actually dealing with any of the underlying issues much harder; anything that the admins do which is or might look anti-The_Donald can now be spun as "another example of their bias". And since we've already got such a glaring example of that bias, the claim is now plausible in a way it wasn't before.
Should have just quietly banned the sub and moved on. Or not banned it and ignored it. Anything but this.