So imagine yourself in the most inconvenient possible world where Omega is a known feature of the environment and has long been seen to follow through on promises of this type; it does not particularly occur to you or anyone that believing this fact makes you insane.

When I phrase it that way - imagine myself in a world full of other people confronted by similar Omega-induced dilemmas - I suddenly find that I feel substantially less uncomfortable; indicating that some of what I thought was pure ethical constraint is actually social ethical constraint. Still, it may function to the same self-protective effect as ethical constraint.