A lot of really talented kids have been told from an early age that they're the best thing since sliced bread, then they're told they need to be more aggressive over and over again, until it's a habit. So, combine a bit of arrogance with a motor that's usually in the "on" position for elite athletes and add a dose of youthful lack of judgement and you get stupidity.
Accounts for a lot of things, not just aggressive behavior, but just assumptions of "right-hood". No, you are not always right, you are not always going to win, and your chances of often being right and often winning probably increase once you learn it. Or as an old friend used to quote, "know when to hold em and know when to fold em".
To be fair, I am editing to add that this may or may not have been the specific reason for the behavior in "this" case, but it is a plausible and accurate reasoning in many cases.
