Which superpower is going to nuke us?

Depends which period said knights were from. Sure, they were all ruthless when it came to it, but some periods more than others.

Take the Crusades - can't remember which crusade it was, but a group of Knights (English, European) completely massacred a town of thousands of men, women and children. Absolute bloodbath.

William of Normandy's Knights razed the North of England on William's order because or something or other... slips my mind what it was. That was bad for the economy, big style.

Oliver 'Ironsides' Cromwell and his army (whilst not Knights in the strictest sense, they were close enough. Early muskets, aye, but the footsoldiers also had swords and pikes, and the cavalry had swords) decimated the Irish during their rebellions. Another massacre.

When most people think of Knights, I'll bet your bottom dollar that they think of Knights such as those of King Arthur. Tudor Knights, Stuart Knights. High on Chivalry. Jousting tournaments, Lady's favours (that is, silk scarves and what not), Quests to Finde Ye Olde Objecte. The Knights of Fairy Tales.