I don’t think it is autonomous rationalism to begin one’s apologetics with theological proofs. The whole point of beginning with reason is not to start from a neutral ground where all facts are brute facts and everyone agrees that religion is not an issue. The point of beginning with reason is to demonstrate the necessity of faith. One must differentiate, as St. Anselm did, between an “independent” argument and an argument made directly from Holy Scripture. Neither can be called “autonomous.” Both presuppose the necessity of the Triune God.