Just walked in on my mom (rant)

Doing something that I can't believe why anyone would do something like that to their own daughter ....
Okay so my husband was in the room and I told him to watch our baby since she was sleeping so I could go eat . I came back to get my vitamins and he was laying in the bed watching her in her bassinet so I left to finish my food. When I came back I was shocked at what I saw, as I opened the door he was standing next to the door and my mother stood up all quick I walked past him and looked down I saw his penis out and I gave my mother this look and she was like " he made me do it " and I looked at him and said " I cant believe this " and went to sit down he quickly came to me and started apoligizing and saying that she bearly started doing it when I came in. She had left the room when I looked. He told me that's why I shouldn't leave him in a room alone with her because he had mentioned that a couple weeks back when I let her massage his back(since she's good at it and knows how) , It bothered me to see she had sat on top of him , I said " MOM " and I forgot what she said but I had left and he told me that he was creeped out because she started rubbing her vagina on him saying " im so horny " my " mother " keeps on trying to talk to me as if nothing happened and i'm NOT okay with that , she keeps on following me to whatever room I take my baby in & I know that I should be mad at both of them but at least he admitted to it I hate how she said " he made me do it " like he didnt make you do anything you did it because you wanted to it didn't looked forced if you didnt want to do it you wouldnt have done it ! like have some respect especially for your own daughters husband .