From what I've seen, most theologians don't even believe that they know how to defend what they believe. The most common sentiment among them seems to be that the part of theology that seeks to demonstrate the existence of God is the crudest and least interesting part. Those theologians who do bother to try and support their belief with arguments, like Swinburne and Plantinga, rarely agree with one another.
In any case, comparing theologians to physicists as you do is silly. Physicists are the experts of physics because they know about the most accurate the...