A commenter on the hoasca exemption thread writes:
So if my religious precept is that all infidels should be killed or thrown in jail and all girls should be given clitorectomies the government should not be compelling me to violate these precepts? Obviously there are all kinds of limits on the things people can do in the name of religion. I don't see the logic in excluding drugs from this if society has determined that drug use is harmful and is subject to a general prohibition.
Here's the thing: Society, as represented by the aggregate judgment of Congress, did not determine that drug use is subject to a general prohibition. Rather, Congress has determined that drug laws -- alongside pretty much all federal laws -- should be subject to religious exemptions when courts determine that the law (1) substantially burdens people's religious exercise, and (2) granting the exemption doesn't sufficiently undermine any compelling government interest. That's the Religious Freedom Restoration Act, passed by such a broad bipartisan coalition that the vote was unanimous in the House and 97-3 in the Senate.
So the "limits on the things people can do in the name of religion" are (as to federal laws) supposed to be set by courts, at least in the first instance. Congress could, if it wants to, carve out some statutory field -- such as drug law -- from the scope of the Religious Freedom Restoration Act, and keep courts from carving out exemptions. But it hasn't. (I discuss all this in very great detail in my A Common-Law Model for Religious Exemptions article, which argues both that jurisdiction-by-jurisdiction RFRAs are generally a good statutory rule, and that Employment Division v. Smith was right in generally rejecting religious exemptions as a constitutional rule.)
Now some might well think that RFRA shouldn't have been enacted. But now that it has been, they can't appeal to "societ[al] determin[ation]" that federal laws should be uniformly enforced, including against religious objectors -- no such determination has been made.