My dad thinks swastika stickers are funny

My dad is a fan of pranks. So, he had an idea to put swastika stickers on things around the house, thinking it'll be funny when someone sees it. It is not. I told him it's not funny and that he should stop, but he thinks it's the funniest thing ever (it isn't). How do I get him to be more considerate of others when it comes to his pranks?