Dear Is Mise,

If you were a saint then you would turn the other cheek instead.

But as neither of us is a saint (yet), we must make an allowance for self-defence (or for defending your dependants).

Even then we should not do more than is needed to avert the danger. In the case you described, breaking the knife-arm is not even a compulsion, it's only disabling an offensive weapon, so no compulsion was even needed.

The spirit of what you do is very important, at times even more than the external act itself: it was never your intention to compel anyone - you simply wanted to defend yourself.

Real saints don't turn the other cheek, that's why Christ's apostles carried swords.

Dear Is Mise,

Weren't Jesus critical of those apostles?

John 18:10 - Then Simon Peter, who had a sword, drew it and struck the high priest's servant, cutting off his right ear. (The servant's name was Malchus.)

Then immediately,

John 18:11 - Jesus commanded Peter, "Put your sword away! Shall I not drink the cup the Father has given me?"

You entirely miss the point (NPI), Christ was well aware that his men were armed and indeed he had earlier advocated the carrying of swords, his admonition of Peter's action was not for the action itself but because it tended to attempt to thwart His and his Father's wishes in the matter of Christ's destiny.

Also, in Christian theology, he knew what Peter would do (being God and knowing all things) yet he allowed him to go ahead.

Dear Is Mise,

It is one thing to carry a sword, yet another to use it.

Yet even if Jesus accepted the use of swords by his disciples, this would only indicate his tolerance and recognition that his disciples were not saints so they shouldn't be expected to pretend that they are.

So much for defending themselves, but when they attempted to protect Jesus himself, that had to stop: Jesus was not their dependant and if he wanted protection then he could easily obtain more than twelve legions of angels.