Despise, disgust, and worry

I've written before about my feeling towards my mom's live in. I've never voiced any of these opinions to him, and unless she ever leaves I won't. However, last Friday when she came over to watch my children she had a mark on her neck. Only one year ago she had surgery on her neck and now she is without insurance to be seen again. She told me what happened and of course asked me not to say anything because he would only raise hell even worse. I sat and fumed about it all weekend at work. It kept creeping back into my thoughts. Yesterday I called my mom and he answered saying that he was just about to call me because he didn't know where she was. I asked if everything was ok between them, had they had a disagreement. He said no and I assured him that if she contacted me first I'd have her call him. Then later in the afternoon he called again. Still no word from her, then he had the nerve to try to bad mouth her to me. The fury resurfaced in a big way. I was trembling. I very calmly explained to him that she probably just needed a break and that is why she isn't answering. He kept on and I lost it. I was very respectful and calm about it, but I told him that I saw the mark even though she wouldn't tell me what happened ( I lied) I had a pretty good idea. I told him that I often hear him giving her a very hard time in the back ground when I call her. That she is getting old and needs rest. He had the balls to say that I don't know how SHE speaks to him. I told him based on what I've witnessed it is probably deserved. He then says he has never laid a hand on her! I reminded him of his little stint in the big house for domestic violence towards her. He got upset that I brought up his past. Oh well. I apologised for being disrespectful and told him it would be extremely unfortunate if I EVER see another mark on my mother. Then Mylie wanted to talk so she did and I hung up. I was worried all night and had an upset stomach thinking about it. I finally spoke to her. He lied about what was said and did fuss a bit, but that's it. My rage still fumes.