mom and boyfriend mad

So my mom is mad at my boyfriend because he said something disrespectful playing around and she took it too seriously. She and her husband always saying disrespectful things in a funny way too. But he did it this time alittle more and now they all mad. What should I do ? My mom sometimes dosent like him or she has been faking it. Her husband I can tell he fakes it too. My boyfriend always has been goofy but not with them because they take it seriously and helps them way too much to keep them happy. He makes me so so happy but it did hurt me that he made my mom sad. But it has also made me sad that they call him fat or different things making them in funny jokes.