Originally Posted by You want to go where?

This is, of course, a complete overstatement. People are not chained into their cabins. While movement between cabins is discouraged, it is perfectly all right for passengers to shift seats at the request of a flight attendant. In the scenario presented by the OP, clearly there is an exigent circumstance which could require the movement, although as other posters have suggested, the obvious solution is to bump the inappropriate passengers out of the exit row and leave them empty.

I would also add that this idea of no moving between cabins is only true for American airlines, with their rules-based approach to security. First and business class customers frequently take trips "down the back" on European airlines for light exercise, etc.. The restriction is only moving up in class, not down.