You're acting a jerk, I see (for all to see, really), but it's simple math. If a character can shoot his bow and move, he's basically firing the bow in 3 seconds and moving the other 3 seconds.
This is what gets most people.
3 sec is an approximation and not a rules/absolute issue.
Or, if a character is limited to one standard action, which is half a round, he can fire his bow.
Not 1/2 a round actually. A standard action takes more effort than a move action which is why you can substitute a move action for a standard action but not the other way around.
It stands to reason, logically, that a character could fire his bow twice in 6 seconds.
D&D combat is an abstraction - trying to apply too much logic will mess up the game totally.
In 2nd ed bow attacks worked differently - in 3.5 the number of attacks is based on BAB (in 2nd ed it was based on class and level)