You don't impart the feeling that you understand the Constitution. That people would begin not to understand what the Constitution is about was always a danger of the liberals precedents of circumvention. And: Voilà! There you are and prove it.
Here's how the Constitution has been interpreted with respect to this topic.
First, the Constitution protects religious belief. That is, you can believe anything you want. However, the government can burden the
practice of religion if the burden meets the following balancing test:
1. The government action must have a secular purpose
2. The primary or principal effect of the action must not be the advancement of religion; and
3. The government action must not foster excessive governmental entanglement with religion
So in a case such as this, the government prevention of the abuse of a child clearly meets the standard of having a secular purpose because 1) Child abuse is illegal 2) children are afforded special protection due to their physical and psychological vulnerability. On the other hand, one could argue that it is an interference with one's religious belief in that the given religion may mandate beating a child for certain offenses. However, given the weight of each argument, along with government's and public's great interest in protecting the health and welfare of children, the second argument doesn't carry much weight.
Second, allowing the beating of children could be said to be an advancement of religion, or at least a permissive maintaining of it. Either way, the second prong of the test is easily met if the government bans the excessive beating of a child.
Third is where a lawyer might make some hay with a very sympathetic lower court because the government, by stepping into the situation does entangle itself in a religious issue. However, the operative word here is "excessive." So the question becomes whether prevention of excessive physical beating of a child constitutes excessive entanglement. I will now cut it short and use the conclusory statement, "This is not excessive entanglement." But it is the most interest portion of the analysis and could take up several paragraphs.
That's how the Constitution works in this situation. Again, much of what I wrote here is conclusory--it's a short peek at how this issue would be analyzed. A serious and thoroughly researched appellate argument could consume a good 25 pages (or more).