Eating poo and christian ministry

After a long and serious conversation with our youth minister, we came up with an appropriate analogy for the kids, to try and explain to them why we are constantly on their back about being counter-cultural, about reading the bible, about turning up to church.
It is not just because these things are right. It's not just that they should do them. It is because these things are good for them, and we love them.
"It is like we are telling you to not eat your own poo".
Sure, you can if you want to. But there are better things to eat. It isn't that we get angry when you don't, we just get sad for you.
Not following Jesus is like eating your own poo.
It also can be abbreviated into disturbing hand actions.