It weird how people gradually accept ideas that seem wrong at first.  
First comes: Exposure
Then [hopefully] an additional exposure to the idea will come along and reinforce the original idea creating an openness to the hearing more.

I do this with my kids.
A pastor does this with his disciples.
-In a healthy society it will continue on with a teacher, a doctor, a news source, a book or magazine article etc.

All you can do is gently suggest and hope the idea takes root in their mind.
🍻🧡👊🏻🥩