I inadvertently posted my answer before trying to respond to the question: "Do you think they were justified in killing Julius Caesar?"
This seems more like a historical question. Julius Caesar was actually assassinated for many complex reasons which Shakespeare could not deal with in a stage play. In the first half of Julius Caesar, Shakespeare makes the audience sympathize with the conspirators, largely because Brutus is the leader and seems like such an honorable and sincere character. But then Shakespeare, in obedience to actual history, turns the play completely around and makes the audience sympathize with Mark Antony and Octavius because they were, after all, on the winning side in history.
I don't know whether I think they were justified in killing Julius Caesar. I don't think Shakespeare cared especially whether they were right or wrong. He was just trying to make drama out of real history. We can sympathize with Caesar, with Brutus, with Antony, and with Octavius, but...
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