I am against licensing parents but the his post is interesting because it makes it clear that there is a stronger argument for licensing parting which we do not license than professions that we do license.
I it is better to give everyone a license to be a parenting and then have rules that if broken result in loss of license. That is everyone has a right to be a parent but that right can taken away in a case of abuse which is the system that we have. I think the same for professional licensing but in professional licensing their might a case for a very easy test (that any college grad could pass with a few weeks of study) up front.
BTW related I think that anyone should be allowed to buy most medicines without a prescription but that one should have to pass a simple test and commit to taking the full regime to get an antibiotic.