They don't want to even have the discussion and discourse in the first place. Period. That's why they're trying to ban it through legislation.
Now, within the field of Critical Race Theory itself -- there should definitely be room for plenty of dissent and debate amongst academic minds and students. Critical Race Theory should be a forum for difficult and robust conversations...what it *shouldn't* turn into, however, is one monolithic set of dogma, reminiscent of what you'd find in an orthodox religion or a cult.
But the Far Right seeks to disallow any such dialogue altogether.