Cassius suggests that antony should also be killed. why does brutus oppose this idea

"Our plan will seem too bloody, Caius Cassius,
To cut off the head, and then hack off the arms and legs,
Like anger in death and jealousy afterwards,
Because Antony is but a limb of Caesar.
Let’s be sacrificers, but not butchers,"

Brutus is an honorable man. He doesn't want to kill anyone else other than Caesar if it's not necessary. He only killed Caesar because he thought that was best for Rome, it's not that he wanted to kill Caesar.