A group of individuals make a Dumgreement on a very stupid plan or decision. Whoever is in charge convinces others it is a good idea. Blindly following the genius who thought of the idea even though it is stupid, a moron mob forms and carries out his plan. The plan backfires, unforeseen repercussions piss a lot of people off and the moron mob makes another dumgreement and decide
the best thing to do is deny
involvement and lie about
everything.
If you make a Dumbgreement before thinking it through bad things will happen, be prepared to cover up your stupid plan.