I'm pretty sure he is calling into question the claim that "it was dangerous to question that the existence of God could be proven through reason", which was a very common belief throughout most of the middle ages and was held with very little danger as far as I can tell

...

This doctrine was supposed (though we don't know if correctly) to be a doctrine that although reason dictated truths contrary to faith, people are obliged to believe on Faith anyway. It was supressed.