In my opinion, "Money makes you happy" and "Guns are bad" myths are related. The point of Stossel's critique of the money makes you happy myth is that once one has a salary in excess of $50K/year, money ceases to be a factor in one's happiness. It's a cliche that "guns don't kill people, people kill people" but it's a true one. Specifically -- unhappy people kill people.
There are two solutions to the problem of gun violence -- take away the guns (which is impossible to do, and unacceptably oppressive in my opinion) or make people happier. Solution # 2 is better by far.
We know that money increases happiness up to the $50K figure. That makes sense -- the national average salary (for those who are actually employed) is about $35K. Someone with an income of $50K or more has more than the average.
The obvious solution is to increase the minimum wage -- but the problem with that is that increases in minimum wage may be inflationary, wiping out the benefit of the wage increase in the first place. Also raising the minimum wage drives businesses that can be re-located to other nations.
The better solution is the decrease the cost of living, implement improvements that make it so cheap to survive that money is no longer a factor. Gov'ts role should be to enact policy that brings prices down. Once the optimal cost associated with maximum happiness is brought down to the point that the average full-time McDonald's employee can afford it, violence will be rare.