That's a valid point. I'm sure many men deal with this issue, and it can be very frustrating for them as well.
How bad is it? Is she expressing her disapproval to you or him? I'm a big believer in setting the boundaries from the get-go, and communicating to difficult mothers that any disrespectful behavior will not be tolerated.
But I also believe that, in most cases, that communication should be coming from her child, not the spouse. Otherwise, it will breed more conflict. It's on you to set your mother straight. Even though she doesn't agree with your choice of husband, it's your choice. She either has to accept it, or accept the fact that it will negatively affect your mother-daughter relationship. So which one would she choose?