I don’t think they realize how they are making people feel. There are first cousins, even in the U.S., who are happily married, but especially there are many around the world, in cultures where first cousin marriage isn’t frowned upon at all.
I get so frustrated. People are so uneducated about this, and then popular culture just keeps making it worse.
Don’t let it get to you, Anon! That’s wonderful about your parents.