Gentleman's Agreement    

Two men know something about each other, that is not known to most and constitutes a weakness, or a barrier. In the gentleman's agreement, the men agree not to point out this weakness, or to enforce action to address it. "If you leave me alone about my shortcoming, I'll leave you alone about yours".

In essence, the gentleman's agreement is a conspiracy — the two men are conspiring with each other to "sell each other out", that is, to compromise each other's masculinity in exchange for an empty comfort.