I would remind you that extremism in the defense of liberty is no vice! And let me remind you also that moderation in the pursuit of justice is no virtue! Barry Goldwater Acceptance Speech as the 1964 Republican Presidential Candidate
Actually, from Aristotle's Ethics I believe. Virtue is in one sense a mean between two extreme, e.g. courage is between cowardice and foolheartiness. But in any given case it is an extreme, for it is the best possible, and we should always strive for the best.