The concept of the separation of church and state came out of the enlightenment and the firm understanding of secularism and religious freedom being the correct foundation for society . The separation of church and state minimises the tendencies of a group that claim to be morally unquestionable, and use this claim to persecute minorities (and/or non-believers) and assume authoritarian rule. We need the morals and methods of any governing party to be questioned at all times. Saying something is gods will or inherently just is unhelpful to discussion and derails meaningful narrative. Do you think that the church should be under the state ?