How to present this to hubby

To make a long story short, my hubby and I got married Nov 2006 and his mother refused to meet me and come to the wedding. She lives literally 15 minutes down the road. Well, hubby said he was done with her blah blah blah. He and I were very hurt by it. Well he does see her by chance because he goes to see his little brother a lot cause his little brother has a bunch of terminal illnesses. Well, Adam (hubby) tells me that his mom emailed him and asked him to go to lunch with her. I'm actually kind of annoyed because he was like "well if she wants to go..." I feel as if he is falling into her trap. I know he still cares about his mom and I know she cares about him, but I just would like a little defense. I did nothing wrong to make her be this way. I feel that he should stand up to her and say if you don't want to have anything to do with my wife, then you don't want anything to do with me... or at least something... and every time I bring it up to him, he gets defensive... I really want to talk to him about this tonight... any suggestions?

Of course there is a lot more details to the story, but I'm at work and can't really be on here long. This is the basic idea.