For the sake of the argument, let's say I want to withhold medical treatment to my children but am non-religious. From what I understand this type of law give the religious parents a privilege that I couldn't claim myself. Because I don't believe in a god I do not have the same privileges as a believer even if those privileges are something as horrible as child endangerment.
People with religious beliefs should not have more privileges than someone without religion. My view is that this is a slippery slope that should never have been started.
Yes, endangering children should be stopped but religious privileges need to be stopped also.

Not to vaccinate is the same as attempted murder.