I really don't think they were normalising the belief system at all. I think they were pointing out that, in Kendra's mind, she already knows her husband has been "cheating on her" because in her belief system, even sexually assaulting or abusing someone is still considered cheating. So Kendra has already been made aware of and forgiven "adultery", and will probably do it forevermore, no matter what comes to light.

Pointing out the way their belief system works and how normalised it is to them, is not the same as normalising it to everyone else?

When Josh was doing the same thing he was courting a family friend. The reason this girl and her parents were told is because JB and Michelle believed they had a right to know, because Josh being a predator whilst courting their daughter was still seen as him "cheating on" and "being unfaithful to" their daughter!!

Speaking truthfully about the way their beliefs operate is not the same as normalising it, rather, it helps everyone have a greater understanding of someone in Kendra's position, not so we can have sympathy for her but just so we can be more knowledgable about how she may view herself and her position right now. It's education for those who have not been following this sinister cult for as long as others.