It's a common issue. My husband is like that and not the baby. He was raised that whatever his parents said was law. I think some guys have a hard time going through the grow up process where the transder their view of their parents from the living doting parents on a pedistal that always know best to they are in fact human and make mistake and are sometimes wrong. My husband is 39 and we've been married 3 years. Don't know your beliefs, but once your married, it's their job to leave and cleave. He becomes the head of the family and his family is now himself and you...and baby will make 3. I told my hubby after a huge blowup with my fil 2 weeks ago that I am not asking but telling him I need his support to back me over his folks. That it's his job as the head of our household. We're slowly working through it and it'll take time....but know you're not alone.
Try and get him to see it from yur point of few put him in Yur place and see how he likes it or talk to him about it and tell him yuh don't want his mother to be the reason why yuh guys split up cuz I've read a lot of story's when the mother in law made a split up and controlling they sometimes r. try counseling it should help.