I think you describe the obvious answer for 95+% of people. And Americans can be relied upon to do the right thing--after they've tried everything else. There's a fraction who will resist the right thing even harder if they aren't "allowed" to try everything else. And another (larger?) fraction that only accept the truth if they feel they've discovered it themselves. So letting them shoulder the cost and try the alternative might be the more expedient way to illustrate how obvious this choice should be. If they can find a way to do it reliably.