Would say there's a difference between protecting yourself and your family from harm and needlessly retaliating. If someone's coming after me or people I love, and only way to stop him from immediately hurting them is to severely wound or kill him, I'll do it.
On the other hand, if he goes after me or people I love but gets caught by the police, and I end up killing him the next time I see him...that's retaliation and at that point I'm acting out of my bounds. It's the place of the law to bring him to justice, not mine.
Understand, I am all for treating enemies with kindness. I'm not saying that that doesn't apply to some random guy who tried to murder you in cold blood. Just saying, when a gun is being aimed at you or some instrument is about to end your life or the life of someone else, I believe it's justified to do anything to interfere with that.
In the case of the martyrs, their total lack of retaliation is a strong testimony to the anti-Christian government they were living under. Many Christians in countries today face the same thing. However, the actions of other believers does not have the same authority as scripture. I can see why they acted the way they did, and admire them for it. And as someone else pointed out, it's rather pointless to try to fight something as strong as the whole government coming after you...at that point, all you really can do is hope to turn some people to God by "killing them with kindness".