I told my wife that was completely unacceptable, and as some people said, I took the high road in not slapping her back. I began an argument with my wife about it, and it got a bit intense. I told her that her mother could not come back, and she got quite angry. I went into the living room and began to cry. This is what gets me. What she did taught him the wrong thing. My son came in, said "Man up, daddy!" and tried to slap me, but he's little so it didn't hurt. But anyway, I got even more furious that he had learnt something from it. The argument ensued. Things are a bit cold. Sleeping on the sofa now but I told my son it's okay to be upset. Buried the dog, and needless to say my MIL is not invited back for a little while.