Potion c, tyranny is not a Brutus' value.
Brutus was well-known for his honesty and morality; he did value his friendships. He used logic and reasoning. Brutus's love of the Roman Republic was more important to him than being a loyal friend to Caesar.
As, Brutus, clearly and logicaly convinces the concerned public that Caesar was a tyrant who needed to be eliminated in order for them to be free, I can assume that tyranny is not one of his values, on the contrary, he rejects it.