I think too much is made of the notion of trying to BE best friends.
As others have mentioned, THAT is something that could ONLY begin to occur LONG after the reverberations from the intial bomb have faded.
I don't think BECOMING their best friend DURING their adulterous relationship is exactly what some are proposing.
It's something more along the lines of being willing to SHOW your spouse that YOU are the FAR better option.
Given the location of your post PDT, I am currently thinking of Sleepers situation where he and his wife are divorced, she is on again, off again with an OM, and he is doing his best to be the better man with his wife.
In my opinion, he is doing a great job of showing his wife just what she has given up. And to me it seems as though it's creating progress between the two of them.
Some spouses you cannot be friendly with. MrsH's husband for example has been a textbook [censored] during their separation/divorce and it didn't matter what she did. Being friendly towards him in order to allow him to see what he was giving up was useless because of the hostility he had inside.
I like to think of it instead as finding a way to be friendly towards your spouse. It takes a lot of fortitude JUST BECAUSE of the betrayal and the pain it has brought. But there are lots of benefits, not the least of which is the possibility that your spouse might eventually realize that you were NOT the ogre they made you out to be in their mind.
I don't know. I think the overriding DB philosophy is, "if it works, keep doing it - if it doesn't, change it." If befriending your betraying spouse is leading to progress between the two of you, keep plugging away. If it isn't, try another approach.
Can't see any reason to suggest that the approach be stricken from the record. Also can't see any reason to make someone feel foolish or used because they have chosen this approach.
Bill
"Don't tell me the sky is the limit when there are footprints on the moon."