Archie, I agree.

1) It was not an overbooking situation. It was the United's decision to deny service to passengers.
2) It was not a denial of boarding, the passengers were already boarded and in their assigned seats.
3) One passenger was injured when he was force-ably removed from the airplane.

The airline had other options, the decisions that they made were even outside of their own Contract of Carriage, which is one-sided agreement written by United solely for their own (not the passenger's) benefit but within FAA guidelines. Lawyer's should have a field day with this and I imagine changes to the Contract of Carriage as a result.