Actually why can't mother in laws just STFU and mind their own business. Everything they also want to put their nose in. They have daughters too and they never thought that 1 day their daughters could be treated the same way as they treat other people's daughter. And yes, their daughter in law is someone else's flesh and blood. What gives them the right to "bully"?

Revenge or for others you are stealing their baby son away. Revenge cos they want to get back the dignity they deserve which is absolutely nonsense. They want to be treated like empress dowager. They want their daughter in law to bow down to them. They want to lord over and control their daughter in law like chess. Very selfish thoughts. Nothing much you can do except either ignore or avoid.