The moral dilemma expressed in this excerpt is: Brutus must decide whether to help in the plot to kill Caesar.
In this speech, Brutus grapples with the implications of Caesar's potential rise to power and the associated dangers it could pose to the Roman Republic. He rationalizes that although he has no personal grievances against Caesar, the prospect of his crowning could lead to tyranny and abuse of power, which justifies Brutus's contemplation of participating in the conspiracy against him.