Dumbest rule in football.

[Beemnseven]

OK, here's another rule I don't understand:

Can someone tell me what the difference is between pass interference and illegal contact (when the defender touches the receiver beyond five yards) ?

One is penalized only five yards, while the other gets the ball placed where the infraction happened. And I know it's not dependent on who the intended receiver is -- I originally thought the pass interference was called only on the intended receiver, while illegal contact was called on any receiver. But watching the Atlanta-Buffalo game, the ball was thrown at a Buffalo wideout, who was touched well after 5 yards, and it was an illegal contact penalty. But why wasn't it pass interference?

Is it simply a judgement call? Or am I missing something?