If Welby took off his frock and gave up his sin-ecures, left the church and then turned around and said this:
… then he’d be showing some sort of integrity, albeit a twisted one. But as a defender of the faith, as expressed in the two books of the bible, he is unfit for purpose and is doubly damned.
The concept of venal versus mortal sin is not so difficult. Let’s step back from the religious and look at it in society in general. If you do something wrong, e.g. an affair, then that is venal – it is weakness of the flesh, it can be forgiven.
If you try to lead someone else into that, knowing it to be wrong, then that is mortal. Welby must know his bible and yet he speaks things anathema to that bible. So he is failing to fulfil that which he was appointed to do.
Which level of Dante’s hell would he find himself at?