Earlier quoted context omitted.
The OP point is still clear. If the law says "You must do x unless you have a religious exemption" then why should anyone at all be expected to do x if clearly it isn't important enough to enforce on all people. If your religion includes killing people, it is still illegal regardless of your religion. So it seems reasonable that any law which can be overridden by a religious exemption should be dropped for all people…
There are established laws that take all it that into account. But new law should be crafted with people's legitimate beliefs in mind. You mention murder but how about something more controversial like a Christian baker being forced to make cakes for gay weddings? How is that not analogous to compelled speech and regulated religion? It is one thing for the government to restrict gay weddings, it is another to enforce…
I don't think this changes anything really. If religious people can use their religion as a valid reason for discrimination, why shouldn't everyone be able to discriminate?
To me, I think everyone should have exactly the same legal rights. Either everyone has to bake the cake or no one does.