I don't want to cut my family off but they keep insisting my husband is gay

I found out my parents told other people in the family my husband is gay. They've been saying this for 4 years even though we both said to stop and it makes him uncomfortable that they insist I'm just a beard. How the whole "Matt is gay" stuff started was when me and my husband were dating he was really really REALLY shy. He turned 21 and had never had a drink of alcohol before. My family wanted to take him out and made a big deal of him turning 21 so the whole club was buying him drinks. Obviously he got very very VERY drunk and it karaoke. So he decided to sing "Hears to Never Growing Up" and he can actually sing really well. I thought it was hilarious and happy to see him let go. He got the whole club lit up. But my parents just thought how he acted on stage was gay because in the part where she sings "kiss my ass" he slapped his ass. And he brought my brother (who's gay) on stage with him. He looked so happy and had a great time. I found it shitty my parents made him feel so bad for it so now he never wants to let lose like that again. They keep saying he must be gay and my mom went as far as trying to catfish him last year. My husband blocked that account right away and my sister told me it was my mom. Now that they're telling other family this and won't stop IDK what to do besides cut them off.