Because what happened before that point was incorrect its hard to jump in and figure out what was right at the later point.

The Player in Seat 5 if he doesn't want to post his blind ought to do something before the cards are dealt.

As to whether he was right or not I have some questions:
1) Did the dealer tell the player to post the blind before the deal began?

2) Did the Player in seat 5 look at his cards before deciding that he wasn't playing his blinds.

If the answer to question number 1 is yes then it seems to me there is no excuse for the player to not have said something earlier.

If the answer to question # 2 is yes then we need Al to come over and kick him in the nuts.