It's kind of a question of how you balance being humane and not draining tax money, right?
* ignore them, let them dumpster dive / beg, and pay their ER bills when they show up at the hospital
* shut them away in a loony bin, and deal with the various expenses of giving them humane living conditions
* housing projects + welfare benefits
All of those expose the community to financial risks/obligations.
It really gets down to the question, "If a person is starving/freezing to death on your doorstep, do you have an obligation to take them in, give them food, and treat them like family?" That's a pretty damned controversial question, and a lot of people feel justified in believing that they deserve everything they own because that's the way nature works (i.e. if you don't compete, you die). Is there a way to "prove" that no one should be allowed to subscribe to social darwinism?
I'm inclined to think not -- i.e. it's up to the individual to decide whether they value that aspect of nature, and anyone who really cares about having a social safety net should just pay a separate tax that gets divvied out to the appropriate charity orgs (+ have the amount of tax vary based on how many people are signed up to pay it so there's always enough money in the fund). If you really think it's "wrong" for humans to be subject to the laws of nature, just pony up yourself; don't feel entitled to steal other people's money if you can't convince them you're in the right.