Please don't dodge the point. There are, or at least have been, religions which practice human or animal sacrifice. I'm assuming you wouldn't argue they should get a pass in the name of religious freedom. Surely you can see that the point of the first amendment isn't to protect religious practices when the come into conflict the law. The point is to keep the law from targeting religions.
And, like it or not, there are still religions that practice animal sacrifice, and the Supreme Court has ruled that laws that prevent animal sacrifice cannot be applied to Santeria churches because sacrifice is an integral part of their religion.
When a law is not aimed at religion, it can require or forbid actions that conflict with a person's religious beliefs. However, when a law is aimed at religion, a first amendment violation usually occurs. In the case you cite, the latter occurs. The law that was passed was created specifically to impede the practice of a certain group's religion. Plural marriage is a form of religious practice for some. However, those people do not enjoy exceptions to the laws that prohibit polygamy.
Exactly. Attempting to do anything more turns the first amendment inside out and sets government up as the judge of what constitutes legitimate religious practice and what doesn't. Typical of so many misguided constitutional interpretations is implements the very thing the founders sought to prevent.