You do not need a degree in "history" from an accredited US university to be a historian. It just helps. I have a degree in history and I don't consider myself more of a historian than Azlan who has done more critical religious research than I ever will. Anyone who disregards him just because he didn't go to some junk colleges and pay enough to get a few degrees in history from papermills just wants to avoid debating what he has to say. And I say this as someone who very much disagrees with his views on the roles of women.

It depends on who is doing the defining, but there are plenty of esteemed academic history journals and university history departments that will accept people as 'historians' who don't have post-grad or even under-grad degrees in history, so long as they have produced enough decent and original peer-reviewed research or analysis. The idea that you need a history degree to be an historian is becoming clearly outdated in this day and age where the internet allows for the democratisation of access to sources etc. the emphasis is shifting to academic rigour and producing original work, not what a person's education background happens to be. That doesn't mean that history teaching at University isn't still central to the discipline, it surely will be for a long time to come, just that it's not a closed shop, it's possible for people with backgrounds to other areas to enter if they can produce work that stands up to scrutiny.

A major recent cross over is people with science backgrounds writing and researching the history of science.

Does he actually call himself a historian? I was always under the impression that he was actually a theologian.