I felt that it ruined the pace of the movie simply to live up to some sort of stereotype where someone on the good guys' team has to die. I'm not even sure this has something to do with the fact that we don't see how the Autobots got captured. Ultimately it felt like bad writing, as if the writers just put the idea in at the last minute or something. Maybe it's just bad editing. But the fact that the movie goes from an Autobot comeback to a staged event just so someone can die just really bugs me. It was an effective scene but the death of an Autobot could have been better integrated into the film.