If you find some Far Side character crawling through the desert about to die of thirst and you can save him without endangering yourself clearly you should do so. Not to save him would be terribly immoral, but should it be illegal? Free societies allow their citizens to do immoral things all the time without tossing them jail.
Unflinching libertarians will argue that a government shouldn't force you to help the dying stranger but I'm sure just about everybody else would disagree (including me). This isn't a post about how evil libertarians are; they'll cheerfully point out that they'd help the poor chap and argue that under their system more people might get saved because the average person has no incentive to avoid the edges of stranger infested deserts. Libertarians don't hate the idea of helping, but they worry about some dork forcing them to do stuff when the case is less clear.
I think this silly example helps distinguish between different types of liberals. In the real world there are millions of cases that resemble the desert example; people die deaths that rich people could stop, the only difference is that we don't see it in front of our eyes. The trouble is that saving people can be very expensive; feeding a starving man is one thing, the latest cancer treatment is something else entirely. What about somebody who has food but of such a poor quality that he is vulnerable to diseases which could hasten death? What about an elderly person who would die in a few weeks no matter how much is spent on medical care?
Once you start forcing the rich to save people it is difficult to find any principled place to stop and any country that has welfare programs less generous than Sweden looks heartless. I think its one reason left liberals differ so much from libertarians. It's also a challenge to people like me who fall somewhere between the two. I'm in favor of a basic minimum income for everybody so I can't offer a principled and opposition to taxation, but I also know that people will continue to die preventable deaths (of course this happens anyway, the important thing is principle!)