That's what bothered me the most in the movies, especially as they progressed. Optimus was outright throwing lines like, "We'll kill them all!" and "You die!", and outright executed Sentinel Prime and Megatron in DotM.
Growing up with the cartoons, Optimus to me was a leader who inspired through courage and bravery, rather than being defined by war. Whilst the movies have a more edgy tone, I felt movie Optimus was the opposite personification of what he should be. Even Peter Cullen described voicing Optimus as a gentle leader, rather than one who yells and screams.