If you witness an individual stealing your property, but they're not physically threatening your person, what is the justified course of action in response?

This is in response to the this thread and the story it links to.

One argument I saw in this thread goes something like this: If you see someone steal the radio out of your car, you "have the right" (it's unclear to me if people mean legal, moral or some other kind of right) to attempt to get your property back, including the use of force. If the perpetrator then defends himself from your attempts (your assault?), and physically threatens you, you then have the right to defend yourself, to the extent that you might seriously injure or even kill the perp in "self-defense".

Personally, I think this is ludicrous... IMO, and I think in the eyes of most state law, it is not self-defense if you instigate a physical altercation in a situation where you're not under duress. That someone has just stolen from you does not give you the right to assault them.

But on the other hand, what should you do?

You can call the police, but in many cases you're not going to be able to identify the perpetrator and they'll escape with your belongings. Is that just the way it is?

I want to say that no property is worth another human being's life. I want to say I would never kill someone to protect my property.

There are some things I might irrationally defend with force, such as my late father's guitar, that has extreme sentimental value to me. I might use physical force to protect that item. But I'm not sure that after the fact I would say I was morally justified in doing so. I would say that I was emotionally driven to defend it.

I'm really curious to see what people think. I was really alarmed by some of the positions in that thread.

edit: some choice replies from the other thread BeingDS Gunwild