The rational part of me agrees that you need to sit down with your husband for a serious conversation and get to the bottom of this. The emotional side of me is angry that your son was treated that way. Not only is it extremely unhelpful and unfair on the little boy, but it doesn't give him the comfort and reassurance that he needs. Nor does it teach him to help deal with his fear. Instead it says that his caregiver, the person he should be able to rely on so he can feel comfortable enough to develop positive coping mechanisms, is unreliable and aggressive. If someone treated my kids that way I'd probably be the one reacting aggressively.

As far as the kid sleeping with his big sister - this doesn't seem like a big deal to me. If you wanted to encourage him to sleep in his own bed, the way to do this would not be to scare him further. I might let him stay for awhile but encourage him to go back and teach him ways to not be scared. It should be a positive and proactive event. Not a time to explode on a very young boy who's relatively new to the world and all it's intricacies.