Is this obstruction on the batter?

[wheels01]

A situation occurred in a men's baseball league and I wanted to get some feedback on interpretation of the rules.

Game is 3-2 home team winning in the last inning. Visiting team has two outs, runner on 2nd. The runner attempts to steal third and the catcher throws the ball into left field, allowing the runner to advance home to score what would be the tying run.

The umpire calls obstruction on the batter, ruling him as the third out of the inning and the game is over. When questioned on the obstruction call, the umpire states the batter did not make an attempt to get out of the way so the catcher could make the throw.

When consulting the rule book, it states the batter is only obstructing if he leaves the batter's box and hinders the throw. The umpire then gets out his case book and says the batter must stay in his stance after the ball passes. He says that because the batter simply raised up (straightened his legs), he cause the catcher to double pump and make a bad throw - therefore constituting obstruction. (He says this is a judgement call, not a rule infraction).

So, what's your take on this?