So, what you're saying is that individual rights should mean nothing if the state believes there's some random good reason to step on them. Woohoo! I like the way you think.
The difference between all those and this particular case is that the parents were potentially raising a future nazi, but no action had been taken that affected OTHER people YET. That's where the state stops working towards egalitarianism and becomes Thinkpol.
Your willingness to have your criterion replaced by whatever society deems "correct" at any given time isn't shared by everyone, fortunately.
Wrong. It's based upon two idealistic dogmas, both closely related. First, the idea that the state can do whatever it sees fit to pursue a policy of absolute "equality", which in turn, is only possible if the Rule of Law stops applying to it - this potentially renders every other single individual freedom meaningless. That's why we have a system, you know? To avoid individual (and collective) excesses.
The second idea is that the state must do whatever it takes to ensure social equality, for everyone, at any cost. That simply doesn't work, it's Utopia. If a balance between welfare and individual freedoms is to be had, inequalities will always exist. Yes, it's a shame that some children will have to grow up under terrible but law-abiding parents, but no system is perfect and it ultimately comes down to the proverbial lesser of two evils. THAT is rational, refusing to accept the shortcomings of an imperfect system and aim for the unattainable is NOT.
That's all good however since all attempts to apply those ideas to the real world have been met with outstanding success, right?