I've worked for a few employers who fit this description, but one in particular. I honestly believe you may be a little powerless in such a situation, as it's next to impossible to change people's behavior and personalities. You can attempt to sensitively communicate your frustration with your boss's behavior, but most likely will only feel resentful, protective, and defensive. The best approach is learning how to deal with this situation and circumstance internally without exasperating it externally. Let go of trying to control the situation. This may not be a permanent solution to your problem because most likely there isn't one.

When you say emotional, what do you mean here? Does your boss yell at you or verbally abuse you? There's a difference between someone who's being emotional, and someone who's a bully. If the former, don't take it personally. You may want to ask others if your communication might be partially to blame too.

If the latter, get out of that job pronto.