not surprised... good thing i have never lived in SE iowa
I don't know the umpire, and don't really know this specific situation. However, the official in me thinks the umpire was probably justified. Also, note that the umpire did not really "eject" the crowd. The fans are not players and technically not part of the game. However, if fans are so unruly that they affect the game, the umpire can ask administration that they be removed. Note the police were called. This means the unruly fans refused to leave, or only left after threat of prosecution.
I've never personally kicked out an entire crowd from a game, But I HAVE had individual spectators removed from the premises, typically by calling the cops. Those kind of fans ALWAYS do something to merit themselves getting tossed....umpires normally bend over backwards to ignore fans for the most part.