At least one study has shown that it isn't out of the question that electronic devices can have an impact on cockpit GPS systems. Inherently this is really only vital for landings.
But the rule isn't really the problem. The problem is cheating.
Day in and day out we all abide by questionable rules not because we agree with them, but because we are civilized human beings. Flaunting rules which could, even in the most remote chance, endanger not just your life but the lives of everyone around you is bad. Forget politics, forget gender, forget class, forget intelligence. If you aren't going to abide by the rules, then don't play the game.