Mother doesnt like S.O.

My mom doesnt like my S.O. because the first time they met him he was shy and didnt talk to them much. But they mostly dont like him because they say hes slow or think hes slow. But hes really sweet and actually pretty smart when it comes to many topics. My mom keeps telling me that he doesnt match my intelligence that im smart with a degree and i need better. But even if hes "slow" hes in college studying criminal justice making a solid future for himself. It sucks that shes judging him harshly. But any thoughts? Advice?