In many states deadly force is permissible to thwart a robbery subsequent to a break in of a domicile
I'm aware of the "castle" doctrines. With regards to these statutes, there's normally an automatic presumption of serious bodily injury or death when the person is in your home. That doctrine has been extended to your car & business in my state (TN).
In some states, the disparity of force is a consideration, and in some other states, so long as the VICTIM can conclusively ("reasonableness standard") express that he or she was in grave fear of his/her life, deadly force is permissible.
What is so hard to believe about those things I've outlined?
Exactly what I mentioned. There normally needs to be a reasonable belief of serious bodily injury or death.
To me a purse snatcher doesn't meet the criteria unless he displays or emphasizes he has a weapon during the strong armed robbery attempt.
We're talking about a purse snatcher and you introduced several other examples where the use of deadly force would more likely be justified. Such examples as forcible rape or kidnapping of a minor, home invasion, and any time a person is in fear of serious bodily injury or death are fine with me when it comes to the use of deadly force.
Like I mentioned in my first post, I don't see the same with a purse snatcher. Although it's a robbery by definition in most states, if I was to shoot a purse snatcher as a LEO with no threat of a weapon or serious bodily harm I'd likely lose my job and a wrongful death action. Many courts follow the TN v. Garner standard when it comes to felonies & deadly force.