Roman emperors managed to be authoritarian long before Christianity was adopted, and Christianity is much more complex than 'an authoritarian religion'. Indeed it's arguable that it was the use of the religion by the Roman state that creates the authoritarian strain of it that you are referring to.
The reason I didn’t think it shocking that a Roman emperor chose an authoritarian religion is because Roman emperors were notoriously authoritarian.
I agree that it would have been possible to focus the developing religion on its relatively benign aspects, love and charity and all that, but that’s not what happened, is it? I’m having a conversation with someone who thinks “God” actually wrote the 10 commandments, not someone who’s contemplated the history of some ancient myths and drawn their own conclusions about how and why they were eventually adopted by the superpower of the time.
I don’t think I’m wrong about the main message of the A&E story, unless my understanding of what it says has been compromised by dodgy translations. Obey, do not question, do not test, do not listen to any input other than God’s* and avoid, as far as possible, drawing logical conclusions from evidence.
A religious text that can be used by people such as the Westboro Baptists to promote hatred, can’t be redeemed by having some nice bits in it. Nice people will use the nice bits. If there were no nasty bits, the nasty people wouldn’t have a hook to hang their deranged hatred on.
I know that some people (e.g. people who call themselves Buddhists and then burn other people out of their homes) will do bad things regardless, but why would a good and powerful being provide them with excuses?
*Of course, if he’s not manifesting himself these days, you can take it as read he’s talking directly into priests’ and/or believers’ brains (or should that be hearts?)