Accidents and domestic violence can be attributed to ~6% of gun deaths. Looking at just the former, there are at least 500 fatal accidents/year.[1] These are just clear accidents - there are also accidents which are prosecuted, and convicted as homicides - and accidents which are categorized as homicides, but are not prosecuted.

The number of justifiable gun homicides (Self-defense) is closer to ~250/year. [2]

So, your gun is indeed twice as likely to kill someone in an accident, then a bad guy in self-defense. (Never mind that not all of those justifiable homicides prevented violence against your physical person. Killing a burglar who wanted your stereo is lumped in the same category as killing someone who wanted to murder you.)

I don't have much of a horse in the legislature of gun control, but for most people, planning on using their gun for self-defense is a bit like becoming an alcoholic to reduce your risk of heart disease.

[1] https://fivethirtyeight.com/features/gun-deaths/

[2] http://www.vpc.org/studies/justifiable15.pdf