There is such a huge stereotype for homeless people. Some of them, yes are alcoholics and some not. The ones that are mostly can't help it, and their addiction brought them onto the streets.
It's fine not giving money if you honestly do not have any to spare (there are people like this out there). If you can't give them money then I feel you don't have to.
Not all homeless people are bad, heck this guy was actually working for the money he was begging for. He was doing something, unlike a lot of other homeless people do.
I think that people who just look down their noses at them aren't very fair and should realise how bad it actually is for these homeless people.