For me, a guy who can keep his cool in situations that are stressful and/or where many others would lose it is wildly attractive. It shows that he's got enough maturity to keep his emotions under control-- which is always the best way to efficiently deal with any situation. A guy who flies off the handle all the time or consistently responds with an out-of-proportion reaction is just a waste of time. Like really, what are those guys trying to achieve? Black eyes and a room full of adrenaline is hardly a resolution to anything, ever.
Also, sometimes women confuse anger for "passion" which is dangerous, because there is most definitely a distinct difference between the two. Passion is great, but one should be careful not to confuse that with some hothead guy who steps out of line all the time and can't keep his tongue in check.