You don't see a problem with delusional people attempting to regulate the lives of others (using voices in their head that they think are god as the guide)?
Basing morality on God's command is a quite dangerous proposition. You can justify any evil by falling back on God told me to do it.
I would prefer a more rational basis for morality be used for the whole of society.
you should read the link and understand that most or all of it is perfectly acceptable in the US as well.
if a pakistani grocer and a pakistani grocery supplier want to arbitrate any dispute related to their supply contract under sharia arbitration, it's legal for them to do so (so long as punishment doesn't run afoul of other applicable laws, such as cutting off a hand or something - i doubt it would).
same with marriage. if someone decided to get married under sharia tradition and happened to pick an officiant who was not licensed by the state, then they would be religiously married but not civilly married (though common law status would not be far off). and once civilly married, if they got divorced under sharia law, that settlement might be very persuasive to the family court, but not necessarily binding (again, still can't run afoul of other applicable laws).
now, if your argument is that the morality of a iron age hill people doesn't necessarily apply to a cosmopolitan land of comparative plenty, then i might agree with you.
take, for example, pre-marital sex. in a society with complicated family webs forming the basis of society, in which excess mouths to feed would cause considerable stress on the tribe as a whole, then pre-marital sex could be a problem (also keep in mind that marriage likely occurred much earlier in people's lives, not much pre-marital sex happens when horny teenagers are already married).
but in a society with ready access to birth control methods and comparative plenty, does iron age morality still apply? that's a good question.