As Doubledealer said, this isn't a G1 remake. Try to forget what you know. G1 Optimus isn't the same as Movie Optimus. The audience came to see an action movie. If the Autobots didn't fire a bullet and took every decepticon they encountered hostage, or let them go, it would be a pretty boring movie.

The first movie taught everyone (the general public) that Autobots = good, Decepticons = bad. They fought on Cybertron and they'll fight here. If you haven't liked the way the Autobots presented themselves in the last movie, then you sure won't like the next movie. Take no prisoners.