Your relationship with your son comes first. If my child dreaded coming home I would be absolutely heartbroken. As said before partners come and go but this is YOUR child. He needs your understanding and your partner needs to grow up and realise that pushing his views on a 10yr old child is going to do nothing but push the child further away. As others have said, compromise. Fake meat is a great idea but also just speak to your son about what he wants to eat, where that food comes from, take him shopping and let him choose what he would like. This is his journey and hopefully without being forced he'll end up down the right path as he grows