Parents crossing boundaries!

How do you all deal with parents who don't mind their business.

I'm 26 and my husband is 25 we have been married 4 years and my parents have always been a little controlling but today my dad literally Skypes my husband and I and asked if we were allowing porn in our marriage and to say yes or no. That we were going to ruin our family if we do things that are not biblical in our marriage..... My husband and I have a great sex life and we love and trust each other. I don't know how to tell my parents to back off. I literally have anxiety and mental IBS from the way my parents have been my whole life. Constantly trying to control or convince me I'm doing something wrong.