He said that if he argued with her versions it made things worse. I don't really love it, either, but my fiance is like that. When we argue, I tell him he did something. He will deny it. But if I keep on insisting he did it, then he won't deny it anymore. He just lets me go on and on.
People who do not want to argue and who do not like confrontation have a hard time defending themselves. I see a lot of it in the tapes of this couple's arguments. Johnny rarely has good comebacks for her, which is another sign he's not used to confrontation.
I think he's already denied these things to her and his version has already been beaten down, so he no longer says anything when she insists.
I also think sometimes she gaslights him into thinking she really did do something to her, like when she went on and about the accidental headbutt or the toe stubbing.