I think their reasoning goes as follows. The bible in the inerrant word of god. So if two translations of the bible differ one of them must be wrong. Now there is no way they are going to go back to the original Greek because that is foreign and as everyone knows God is white and speaks English. And god wouldn’t have allowed a flawed bible to be in use for hundreds of years while he waited to put out the correct one, so god must have inspired King James to personally write the correct one.
As an aside, I think my brain has been trying to protect me, but it was all for naught thanks to @Jihi’s accursed link. Despite reading dozens of posts and articles about this I had for some reason always read it as the “God Bless America” Bible. It was only in reading the link that mentioned that the song it was based on came out in 1984, that I realized to my horror that it was the “God Bless the USA Bible” 
, named after my number one top most hated song. Now I hate this bible more than ever.