The idea actually has plenty of merit, on both sides - homeless people absolutely are in desperate need for tools of self defence, but also if anything has proven to get the NRA to support tighter gun control it's people they consider "undesirable" arming themselves.
I'm all for marginalised people being armed, but there is also no doubt that "gun culture" in the US is an entity of its own (evident not only by the numbers and kinds of guns owned compared to other countries, but also the sheer number of shootings that happen) that is running rampant and needs getting rid of.
Guns should be treated as the tool and a last resort they are, not the basis for someone's whole personality.