I would say to ur husband something alone the lines of "I hope our daughter(s)/grand-daughters have loving and caring in-laws and not the type of in-laws that you see in these dramas on TV that are always making life difficult for their DIL's".. Given that you already made an earlier comparison between your SIL's situation and mentioned it to your husband.
Hopefully, that will spark a few thoughts in his head and he would thing again about his actions..