It's not about thief or stuff. If someone breaks in I don't know why they're there. I have no reason to assume they are only there for stuff or won't hurt people who get in their way. Giving them the benefit of the doubt make no sense when they're already breaking in and violating your home. As an example I wouldn't go out to stop someone from breaking into my car or open the door during some incident. But if the door get kicked in a person shouldn't expect a warm welcome.
I do not care if a criminal gets hurt during the course of crimes that violate people's homes and personal safety. Anyone has a right to stop such people with force. Self-defense isn't a crime and I really don't consider it a problem. The gun was not the first resort. There were presumably doors and locks. Maybe some yelling. The criminal choose to victimize someone and found out that goes poorly on occasion.
If you want to prevent violence prevent people from being in desperate situations and commiting crimes against people. Don't expect people to be accepting of home invasion.