You're father in law was a christian, he always thought it was better for woman to dress modesty with only dresses that could cover them up. Which you found stupid but respected it.

You all had a plan trip to the beach( Husband, Father in law, kids, and you) You're daughter who was 24 worn a bikini to the beach which You're found fine but the opposite was with you're father in law..

FIL: "What message are you telling them! And what is she wearing!"