So your argument is that if I can be demonstrated not to uphold a moral principle, then the moral principle itself does not exist?
Hopefully you are aware of the flaw in that argument.
You have no right to make decisions for other parents.
And the parents, in their turn, have no right to make decisions for me.
If their child is dying in front of their eyes and they do not lift a finger to help her, that is their decision. And if a fellow human being is dying in front of my eyes and I do lift a finger to help her, that is my decision.
These parents do not have the authority to rob me of my conscience or my moral agency.
Nothing frightens me more than people who grab control of other peoples children because they know better.
Boo.
And again, that is a liberal argument that preaches YOUR opinions should trump the parents'. If I teach my children that homosexuality is wrong, and a teacher thinks that's "homophobic" and "unhealthy," are you arguing she has a right to overrule my decision?
But I guess since you, in the grand liberal tradition, know better than everyone else you have been given a moral duty to make decisions for others.