I don't know why you would think that he was trying to live the safest life possible through the exclusion of all risk factors from his OP as absolutely nothing in it indicated that. He indicated he does not like guns and that guns are a risk factor for death. His statement is entirely accurate. It makes zero sense to advise him on all other possible risks to human health. Why stop at cars? Why not give him advice on a good diet and exercise regimen? Why not give him tips on limiting sun exposure? Heart disease and cancer are far greater threats to people than cars are, after all.
I don't see why people are having such a hard time respecting the question that was actually asked other than the fact that when guns come up some people get super defensive. His question was reasonable and his position on guns is probably smarter than most people in the US as he correctly identified them as a risk factor that carries little utility with it.
To be perfectly fair, I think that this particular discussion has been the least defensive conversation about guns in a while.
Considering heart disease and cancer can potentially be cumulative, how you live in your 15-44s where vehicles and homicide are the primary risk factors, does not mean that you should forsake good diet and exercise until you enter the age group where the risk factor is most prevalent. So that is also a good point.
With that being said, sitting down for extended periods of time is an independent risk factor for mortality, mainly heart disease. Irrespective of weight and diet, having employment or lifestyle that requires long periods of sitting will raise your risk of dying compared to standing lifestyles and employment.
If you do have a desk job, strongly consider a standing desk, or a motorized desk to limit extended periods of sitting.
Easier than vehicle or gun elimination, sitting elimination is something that really can be achieved by everybody, and ultimately carries the
highest overall risk factor if you combine all age groups and causes of death.