In any group of people, there are going to be some with an attitude like this. But having a heartfelt do-gooder's attitude toward the homeless doesn't really do them any good either. You have to actually do something.
I have a friend who does. And since I've gone with him and groups of high school students to distribute food and clothing to the homeless in NYC, as a monitor, there are a few things people seem to be forgetting here that need mentioning.
When we distributed food, we never used the same paper soup bowls twice. We never allowed the students any physical contact whatsoever. We never gave money, only food and clothing. We never allowed the students to be any significant distance from the monitors and especially not out of sight. The reason? Behavioral problems are much more pronounced in the homeless, and sickness is rampant.
Do what you can. But don't forget, there is a documented risk in being around them. Be human, but careful and you can help them without harming yourself. The best success story is, that one of them married one of the assistants, they now have a happy family, and he has become director of the group. Wow!