He says that if your spouse cheated on you and you want to leave her, you're better off if you're not angry. And to get rid of your anger you have to recognize that she is a (fallible) human being.
Here's what I think he's saying.
If you recognize that people are imperfect you won't expect very much of them and that gives you less reason to be angry at them when they screw up.
In fact, you might be sympathetic with their situation just like you'd sympathize with a little kid who can't do up his buttons.
Andrew says the pain of betrayal can only be satisfied by this kind of basic love. Any other approach will leave you feeling the sting and licking your wounds for a very long time.
"He may have been able to restrain himself from answering betrayal with blind fury because he appears to consider himself not a king but a partner with his own human failings."
Note: I just checked with Andrew Thorn. He didn't tell me I was wrong about what he said. He just said this doesn't sound like him. So I assume I got it wrong. I will track down the exact quotation and post it soon.