On a more basic level, it is about power and influence. I was really stunned to hear that a White House correspondant is paid $350,000/yr. that makes him very important, don't you know? The Sunday media people earn a lot more than the Presidents and Congressmen they comment on, so they must be more important.
It's not news that they are arrogant and disdainful of us "little people" especially at the White House. David Gregory is only the most obvious manifestation of the attitude. And they compete amongst themselves to see who can best trick, trip up or otherwise get the best of the press secretary. Tony Snow is probably the best PS to have right now to respond to their attacks.