What this means is that Mike was a willing recipient of that hateful, ignorant comment about reading between the lines that useless goof of a wife-repellent Arnold made to explain away the fact that his own toxic personality is why he's still single. To amend John's breezy comment about how you can't cheat an honest man, we were dealing with a case of yet another buffoon allowing himself to be lied to because it scratched an itch. Martha's discovery of the fact that Mike was being a butthead because he wanted to believe the worst of her should have alerted her to another reason she's lucky Mike is no longer part of her life:
Foob Fact Number Two: Mike Patterson doesn't actually trust anyone and expects to be betrayed and laughed at.
The reason for this is sadly somewhat obvious. Said reason recoiled in disgust and horror from him when he wanted attention because she was and is too much of a child herself to be a parent.