And bear in mind that the sword was the AK-47 or M4 of its day. It was the standard issue infantry weapon of the time.
Except for martyrdom for your faith, my personal opinion is you should kill to defend yourself and your family. Also to stop someone else from killing like yur neighbor. The Jews came to that conclusion after WWII. Never again will they be led like sheep to the slaughter.
To my way of thinking it would be a sin to let harm come to anyone and you had the means to prevent it. It's also meritorious to lay down your life so someone else might live in certain situations.
Now if the police are harming someone, once I would have said you don't interfere. Well, you still don't interfere if you don't want to get shot or seriously manhandled but that was before I saw and learned some things about police brutality, excessive force.