Why, gunner, why?

Today's quote: It's strange how pulling a trigger is easier than playing the guitar. Easier to destroy, than to create.

Do you ever wonder what possesses some people to do or say the things they do in class? Right now, I am confronted with a very irritating example of a gunner in summer school.
Day 1: I was overwhelmed with the most shockingly violent urge to smack the person as they prattled on about the "genius of the American constitution" or the "great Iowan so-and-so."
Day 2: Someone else in class did the classic cough/stage whisper "Who cares" when the person tried to do the same thing again.
Day 3: The person sat silently throughout the lecture.

Now, it's a shame when someone feels restricted by others from freely expressing themselves, but it's also another matter when they speak of subjects that really bear no relevance to the course. It's also quite disrespectful when the student in question takes on an aggressive stance towards the professor, almost of the attitude that the student knows better. I think I could put up with almost any amount of rambling or going off on tangents, but it's that last part that really pissed me off. I've always been taught that once you enter the classroom you set aside any notions of your own superiority, because it is here where you are a student to that teacher. Sure, teachers are wrong sometimes and maybe some corrections are needed. But the kind of blatant aggression displayed towards the professor seemed very out-of-line to me. I don't know if someone else spoke their mind to that person, but they seem to have temporarily become quiet. At least the professor seemed to bear it all in good humor, even if most of us students most certainly did not.

To a large degree, I've noticed a fair amount of cockiness in law students, but really no more than to be expected. But there is a line that is crossed when that cockiness is displayed to a professor, coupled with an attitude of condescension. What is going on here?