In act 3, scene ii of julius Caesar. Why does brutus say he had to kill caesar

"Be patient till the last. Romans, countrymen, and lovers! Hear me for my cause, and be silent that you may hear. Believe me for mine honor, and have respect to mine honor that you may believe. Censure me in your wisdom, and awake your senses that you may the better judge. If there be any in this assembly, any dear friend of Caesar’s, to him I say that Brutus' love to Caesar was no less than his. If then that friend demand why Brutus rose against Caesar, this is my answer: not that I loved Caesar less, but that I loved Rome more. han that Caesar were dead, to live all free men? As Caesar loved me, I weep for him. As he was fortunate, I rejoice at it. As he was valiant, I honor him. But, as he was ambitious, I slew him. There is tears for his love, joy for his fortune, honor for his valor, and death for his ambition. Who is here so base that would be a bondman? If any, speak-for him have I offended. Who is here so rude that would not be a Roman? If any, speak-for him have I offended. Who is here so vile that will not love his country? If any, speak-for him have I offended. I pause for a reply."