Polygamy - allowing large extended families that are self-reliant, autonomous and authoritative and not dependent on the state - unlike small nuclear families that are always externally dependent. Dissipation of power across families/tribes also emerges as a dynamic as opposed to its concentration in a central state allowing it to be oppressive.
Child marriage - marriage is about more than just sexual relations - the institution allows for guardianship and where this is necessary then there is no problem with such marriages - the alternative is guardianship ("child marriage") is with the state in its orphanages where we are forced to pay for it.
Death for apostasy - societies based on faith see publicised apostasy as treason, seeking to undermine society or create serious public disturbances - they thus apply capital punishments for the same - most states do the same.
Death for zina - families are the core unit of society and those who seek to undermine them commit treason thus capital punishment - there is leniency for those with mitigating circumstances eg single people.
Amputation for theft - the criminal should be punished and not mass society by funding of psychological torture in prisons at our expense.
Women's evidence worth half of a man's - weighing of evidence happens in every legal system - those not involved in social matters as women usually are not in Islamic societies have the weight of their evidence reduced - women who are involved in such matters see the weight of their evidence increased.
Triple talaqh - simpler and faster means of divorce than the bureaucratic and costly means seen in western systems - most contracts can be easily terminated, why not the marriage contract