Everyone does. It pisses me off when women use their periods as an excuse. Okay, so you happen to have external "proof" that you're experiencing mood swings at the moment. But everyone goes through periods of psychological vulnerability, moodiness, whatever you watn to call it. How is it any different?
PMS is a myth, if you ask me. No one is going to be in a fantastic mood when it feels like their abdomen is in a grinder, but other than that (and some special cases that can only be diagnosed by a doctor) it's all BS. Everyone has highs and lows, men and women alike.