Firstly, you are a hero and did nothing wrong. Your BIL was being disrespectful to your son and you put him in his place. I don’t understand your wife’s perspective and frankly why she would not defend her son or you for your actions. Not only that, but your BIL was also disrespecting you and your wife for how you choose to support your child through this difficult time. Obviously your BIL lacks emotional intelligence and was unfortunately probably raised this way. Bravo to you. And your son is lucky to have you as a father.