I assume you are talking about the section where Brutus counsels the conspirators against killing Marc Anthony because it would seem a bit too excessive to the public. This is of course a very interesting speech from Brutus as he ironically counsels restraint against the very man that will be the result of his downfall after Caesar is assassinated. However, Brutus argues that by restraining themselves and not committing excessive acts of violence it will help the public to accept what they are doing:
Brutus imagines that only killing those who it is absolutely necessary to kill will enable the public to think of them as "purgers," people purging Rome of various evil influences for its own good, rather than murderers. Excessive violence and killing would make it difficult for the conspirators to argue that they were merely acting for the good of Rome.