I agree with the idea that one should ask themselves "What would I do if I didn't have a gun?"
I also suggest that a person has no duty to NOT do what they would do if they didn't have a gun just because they DO have a gun.
Confronting someone who is trespassing on your property is a basic right. If the situation is escalated BY THEM to one that requires force, fine. It's their choice.
The homeowner did not start with force. He would have been better off with a concealed weapon IMO, that could be revealed as needed, possibly even in an attempt to de-escalate the situation, which is specifically allowed by law in many places.
Once the firearm is present and the BG presses forward, well, justification of the use of force, including deadly force, would be highly dependent on the typical rules. ie, disparity of force, fear for life, etc.