I tell them about a friend of mine who's father gave him £500 and told him not to darken his doorway until he came "back to The Truth!"
He was fifteen years old. To his Dad's credit, £500 was quite a bit of money back then.
The kid's 'crime'? Questioning his father's religious doctrine. He was a Plymouth Bretheren.
How do we know which one has The Truth?
Easy.
His Dad knows my Dad doesn't have The Truth, because he doesn't believe in the Trinity.
My Dad knows his Dad doesn't have The Truth, because he does believe in the Trinity.
...and they both tell their kids that Satan walks about like a roaring lion seeking to devour people, blah, blah, blah. They both use the same terminology, the same psycological warfare. They only differ in their doctrines.