Well that is another situation. If he has no weapon in hand, odds are I'm going to warn him first. I do live in a small space but I do have an organied plan of retreat. I can easily fall back twice and put plenty of obstacles between him and me.
If he just won't quit coming, he's obviously trying to hurt or kill me. The thing is, is there a good reason to break into some random person's house and threaten them with physical harm of any sort? Surely most of us can be more reasonable than that.
I'm just not sympathetic to these sob stories I've heard on occassion. "Boo hoo the intruder was unarmed and he just wanted to take some jewelry..." My thinking is, why are the same people who criticize the Castle Doctrine the same people who would be outraged if someone broke into their home while they were in it and stole their microwave oven?
But let's take your question and turn it around. Should you ever rush into someone's living space in such a manner?
Now I can see how this could become an interesting problem in my apartment situation. See I have often wondered if I should get involved if I hear a scream or a cry or a gunshot from a neighboring unit. What if the woman next door to me yells "Oh God somebody help me please he's trying to kill me!" at the top of her lungs and I break down her front door and run in there ready to shoot something. Doing that is quite stupid. I don't know the situation, I don't know who the good guys are, and I might have taken the cry for help out of context and wind up getting shot myself.
However could I ignore such a thing in good conscience? I submit that I could not. I would of course notify law enforcement immediately, but when someone needs help right now and you're the only one there, you're going to feel awful when you find out that woman was strangled to death in the two minutes it took for the police to get there. Sure you might not have made the difference, but do you know that?