last time I heard a conversation like this I was 13-15 maybe and I was in your position, and my severely disabled brother who couldn't talk but just make noises was in your sons position. Our father had a go at my brother for know reason, and kept doing so, and threatening him, so he cries (he never cried) I step in and say whats happening knowing quite rightly fathers just really angry and taking it out on the wrong person = me getting the biggest beating I have ever had, which lasted for what seemed to be a lifetime with me being fit to the floor over and over. Mother comes in and sits eating with back to us during this and does not help. On asking her why she didn't do anything she said she thought I must have been in the wrong. If you knew me as a kid well you would know that was a stupid statement as I was a 'perfect' - does everything right, tidys room and doesn't speak unless spoken to kind of kid.
Took weeks to get over the beating, wanted to run away from home but worried about disabled brother so stayed. Brother now no longer with us, died of NHS negligence. At least I can morally remember the day stepped in to defend him, I would do it everyday if it had kept him safe, he was disabled and unable to speak but he was my brother.
And to get back to the point of this story, such an instance you describes takes me back. I worry your husband is under a lot of stress he isn't telling you and be careful it doesn't become physical, or at least worsen.