You can tell a lot about a guy by the way he treats his mom. I think the problem comes in when the mom takes advantage of the son and manipulates him/interferes in his relationships, but I would never be rude enough to call someone a momma's boy.
Perhaps his mom was there for him when his woman wasn't?
As much as it really annoys me when my mum tries to 'mother' me, and it really does, she's always been there when nobody else has.