I’ve heard this claim before and haven’t really been able to dig into it. One question that came up through that article related to this paragraph:
The study focused only on homicide risk and did not examine how living with a handgun owner might increase or decrease the risk of being victimized in other ways, including by nonfatal assault, home invasion, or property theft.
This sounds like something like a home invasion that would have ended in a homicide but didn’t (due to a gun or other reasons) wouldn’t be counted. The cases that are due to a gun would seem especially important.