Is Brutus right to join the conspiracy?

It is possible to make an argument for both sides of this debate. Brutus himself wrestles with the fact that he has always been "Caesar's angel," a close friend of Caesar's and one who was dearly loved by him. He does not want to kill his friend. However, he truly believes that Caesar wants to establish himself as a king in Rome, and that, although he has "no personal cause to spurn at him," "the general [cause]" is a compelling reason enough. He attempts to distance himself from his personal attachment to Caesar by describing him as a "serpent's egg," and those who are loyal to the ideals of the Republic must "kill him in the shell" in order to save Rome.
Later, when he is explaining himself to the assembled crowd, Brutus justifies his part in the conspiracy by asking if they would "rather Caesar were living and die all slaves, than that Caesar were dead, to live all free men?" Brutus says that he did love Caesar very much, but "loved Rome more." He loves his country so much that the death of Caesar seemed, to him, the only way to ensure that Rome would not be subjugated under Caesar's abuse of power.
Even Marc Antony, at the end of the play, describes Brutus as "the noblest Roman of them all," stating that, unlike the other conspirators, it was not "envy" of Caesar that drove his actions, but "a general honest thought / And common good to all." So, although Brutus's part in the conspiracy ends in his own death, it can be argued at least that he believed he was right in joining the conspiracy, and that he was acting out of love for his country.