1. Antony is referring to Brutus when he says his life (Brutus) was gentle. Antony says that Brutus was the noblest Roman of them all, and that he was the only one who killed Caesar for the safety of the Roman Republic. This is seen by the reference "and all of the conspirators save he". Antony implies that Brutus would never have assassinated Caesar, except in order to properly protect the Roman Republic.
2. Honor. Antony shows a great deal of reverence towards Brutus. He strongly believes that in regards to the other conspirators that killed Caesar, Brutus stood alone as noblest Roman. That they "did that they did" was in jealousy of Caesar's power, but Brutus was fearful of the power and did not have a jealousy of it, but a need to stop it from growing to uphold the Roman Republic with honor.
