I just loved that poor Lieutenant Colonel Lennox got his wife and daughter mentioned in the first movie, and then promptly forgotten about in the 2nd and 3rd. The guy does as much as the main characters and he gets relegated to generic-army-guy.
And I think pussy black guy was just a friend of Epps.
All-in-all though...I don't think anyone could blame Optimus Prime for losing his cool in this movie. He had a really shitty week. First he finds out that Shockwave has arrived on Earth, then that the US government has been covering up the knowledge of the Ark on the moon, then that Sentinel Prime has struck a deal with Megatron and betrayed the Autobots, then that his closest friend Ironhide was destroyed, then the United States decides to send the Autobots packing to save their own skins, then he has to pretty much order Cybertron's death to save Earth. No wonder he just snapped and tore Megatron's head off with that axe.