There are so many different traits inherent in different people, that it is very unfair to generalize or base an assumption on stereotypes. The situations in which someone's personality is challenged range from petty fights, to arguments, expression of independent beliefs, achievements etc. But, it is an interesting observation, that for a considerable number of people, the expression of their psychological composition arises during trivial matters. The term 'trivial' here would mean those moments which are of a relatively less importance to him than others to which he gives considerable amount of attention and effort, and this has to be based on his own conception various events affecting himself. This is where the humor part comes in. A lot of us do not realize the amount of unnecessary (or necessary) time we spent behind these situations solely to reinforce the swelled up sense of our personality.
We would not have survived if we were devoid of personalities, but probably to many, the reason they survive is the existence of their self-conceived notion of the best personality. The funny thing is, instead of detesting such a trait in people, (which morality or the books demand from us) we find ourselves adjusting, and at times appreciating such a trait, for the very basic reason that we tend to associate ourselves with that. This is why terms such as 'male-ego', or 'attitude' or in that case 'guts' have been coined. Majority of the people would admit that possessing such a trait is unethical, while realizing or not realizing that even he/she is not entirely devoid of it!
So, when we have a real bad brawl with a known or unknown person who beats the crap out of us, we may swear, shout, hit, fight or (i pray not) even kill the guy (the possibility of which would be very bleak), yet eventually we end up admiring the (scornful!!) "whoever-the-fuck-he-was", and i bet, would secretly love to be in a vice-versa position! That is what ego is all about!