That's when you tell them "We're very sorry if it has to be that way, but it's your decision I guess. However, if you're no longer our child, there's no reason we'd leave you anything upon our death, so it will all go to your siblings (or if no other siblings -- to some extremely conservative charity we respect, probably the Cato Institute)"
It’s hard to be charitable to the lefties, but remember the problem is that the devil has turned them into worry warts.