Possibly, but also possibly not. You could argue that self-defense will lower homicide rates only when enough of the population owns guns to actually start deterring people, and that high gun ownership states still don't have enough guns to lower the homicide rates.
In general I think I agree. A world with half-gun ownership is the most fatal; no-gun and total-gun ownership are probably much less fatal, but I do suspect no-gun ownership is less fatal than total-gun ownership