Husband's family always invites him to dinner then eats without him

My husband's family has always treated him like he's less than them and like he doesn't belong. He is the last to be invited to things and the last to find out news (he was the last to find out that his mother had cancer and that his sister was pregnant). They constantly talk down to him and make him feel stupid when he has an opinion. They treat his cousins and sister as equals so I know that they don't just treat all young people like that. They're very passive aggressive and gossipy and can be very clicky. It's very childish but, I've always looked the other way because my husband loves his family and wants to be a part of their lives.

Tonight they did it again. They have a habit of inviting my husband to "Friday night family dinner" and giving him an exact time only to then eat an hour before he gets there and the act awkward and rude when he eats his dinner. They don't include him in any conversation and look at him like he's rude when he tries to include himself. This very reason is why I decided to bow out quietly and no longer attend this dinner. I can't sit there and watch my husband's confidence be obliterated while knowing that he'd never forgive me if I said something.

Tonight takes the cake. His mother texted me inviting us to dinner at a specific restaurant at a specific time. I bowed out as usual but, I stated that my husband could make it. She acted happy to hear it and I thought that that was the end of it. My husband is excited as usual to see his family and he makes sure he looks nice before going out the door. He gets to the restaurant and waits for them for awhile before finally calling them and finding out that they ate an hour and a half earlier and left already. His mother said that they simply forgot about him. I find that to be impossible considering that she just invited us not even 3 hours before they went and ate without him. He called me on the verge of tears and asked what he should do and I lost it. I told him to stand up to them and tell them that they're rude and inconsiderate and that their behavior is shameful. I told him that he deserved a much better family who never treated him this way. I told him that he should stop going all together and tell them where to stick it. My anger made him feel better but, he says that he doesn't want to hurt their feelings by standing up to them. He's such a gentle soul and I hate to see him hurting. It's taking everything in me not to go wonder wife on their asses and tell them to shove it. What should I do? My husband needs me and I feel that I should stand up for him because he's too hurt to stand up for himself. I just don't want to upset him by creating that divide. When he comes home from getting a special treat (I told him to get as many sweet treats he wants) I'll have to yet again console him as he asks me what he did wrong and why they don't love him as much as his sister and cousins. It breaks my heart. Has anyone been through this? What would you do in this situation? How should I handle this? I can't stand to see him go through this yet again. Thank you for reading and thanks for the advice in advance. 💕