70% of all endo is done by GPs. 50% of all ortho is done by GPs. If general dentists didn't do ortho, there wouldn't be enough orthodontists to meet the need. I personally don't plan on doing ortho, but have no problem with GPs who are willing to put in the time and training to learn how to do it right.
It would be great if everybody who wanted to do ortho would do a residency, but there simply aren't enough programs for that to happen. Sure, there are some GPs who shouldn't be doing ortho, but I'm willing to bet there are quite a few orthos who shouldn't be doing ortho.
From an access to care standpoint, GPs doing ortho is in the best interest of the public.