You nor I may like a particular religion, or particular religious beliefs of certain individuals, but we must protect the free exercise of religion in this country if, for no other reason, than to prevent the state from dictating what is right and what is wrong. When the state defines morality, we, as people of a free society, will cease to be free.I would quibble with this argument a bit -- the state defines morality through the law all the time -- but the basic point is sound not only from a libertarian but also a conservative perspective. Aside from its theological value, religious liberty serves a critical function in limiting the power of the state to dictate moral norms without criticism. Absent religious liberty -- and coherent religious institutions within a society -- there is very little tangible limitation to the power of government.
By emphasizing the autonomy of faith & by fostering an atmosphere where institutions can flourish outside of the micro-managing grasp of the state, religious liberty fosters the practice of limited government. Organized religion and religious believers function to provide an alternative voice to state power. This is one reason why one of the tells of tyranny is its hostility to traditional religion, believers & institutions.
One does not need to be religious to understand this point and to come to the defense of religious believers & institutions when under attack.