To be quite honest, unless you are a very devout Christian, I don't imagine you examine your life and tick boxes as to whether you've obeyed the ten commandments or not.
I believe they provide a guide as to how a decent person should live, and I try to be a decent, honest person and I have, like most people, a conscience which guides me. but as humans we are fallible. Charles is fallible and although the defender of the faith title is the sovereign's, it has been accepted that Charles will defend various faiths. We are a tolerant society and Charles, being human, has made mistakes.
Don't we all make mistakes? Life is messy and the Royal family face the same personal dilemmas we all face. They don't always get it right.
For most of us, our short-comings and faults remain behind closed doors. The Windsors are under the microscope. Most feuding couples play their games away from the spotlight.
I think it's rather strange to want Charles to be a man without faults. He was wrong to hanker still after his dear friend (and lover) Camilla when he was married but he won't be the first man (or woman) to have a bit on the side, and he won't be the last, sadly.
I have been one of the many, many married women to have experienced this. It hurts. Charles hurt Diana, Diana in turn decided what was good for the goose was also good for the gander, and who can blame her?
They are/were humans, not high clergy. In many ways such scandal made the royals more human with the emergence of the paparazzi, having a field day at the expense of those in the public eye.
We have to move on. Royalty has to move with the times too.