Far from a thought experiment, this is the exact scenario for most of the monotheisms. The Bible, for example, which is held to be the ultimate source of truth

Far from a thought experiment, this is the exact scenario for most of the monotheisms. The Bible, for example, which is held to be the ultimate source of truth including moral, contains many passages condemning behaviour we find acceptable today, and condoning behaviour we would find abhorrent. Are its followers violent atavists? For the most part, no.