Because it's just another scare tactic. We know there are some dangers having firearms around.
That's why we want to make sure the goverment isn't the only people allowed to have them. First comes registration, then confiscation, then the tyranny.
Good. Public spaces should be reserved for functioning members of society. 'Homeless' are largely scammers and con men. They choose to reject civilization and they do not deserve to reap benefits that capitalistic societies provide.
I live in a city, with a public transport system, and it's terrible. Nobody but the poors bother with it as it takes HOURS longer than simply driving. This isn't hyperbole, it's actual trip times from actual trips taken.