Government intrusion is unwanted and unnecessary for the protection of Christian Churches. My guess is, most churches could do this well and without spending one cent of tax payers dollars. However, on the judicial side of things, it would be very good for the State to prosecute those doing harm to Christians, especially in worship services with a strict and quick justice. Establishing a precedent that this kind of crime will in no way be tolerated. The State does have a vested interest, wether they know it or not, in the thriving of Christian doctrine and practice. The State does have a God given duty to protect the free exercise of Christian worship. Frankly, Protestants have replaced their older and more biblical understanding of Church and State with a modern and highly misleading one of “total separation of” Church and State. The answer, as I understand it, is the same here as it is in so many other questions springing up in the Social arena today; that is the keeping the Three spheres of divine government ‘distinct’ BUT ‘related’ and all under the headship of King Jesus.
Note: See Westminster Confession of Faith chapters 23 and 31.