DD,
You don't need to have all the answers. I do not either. The slippery slope already exists. Remember when Obama was asked about the zest for life that Grandma has, and Obama said to just give Grandma a pain pill & let her die?
It does not have to be uniform or perfect. It is neither now. Public welfare doesn't catch everything today, so private charities not catching everything later is no different. But there is a huge difference. Today, it is theft. Gov't taking forcefully from individuals and choosing winners and losers. That needs to stop. Instead, private charity are people willingly giving. Whether it's "as effective" or not, at least it is far more fair. Nothing taken from those not willing, and not to any charity that the victim (victim of theft) does not support. BTW, you'll be shocked at how generous people are when the gov't doesn't suck them dry. And it's managed far more efficiently, no gov't overhead/waste. More localized, lots of volunteers.
And if somebody needs particular charity, they should move to where it receives the most support. Drug addict? Around Hollywood should get lots of charity. Homeless? Try California. Escaping prostitution? Las Vegas? Calling it like I see it.
My point is to eliminate the slippery slope of taxpayer-stolen "gov't funded" wealth redistribution. Lock that down. There is a law that a criminal should not profit from acts of crime. Stealing this from taxpayers is the crime to be stopped, so welfare recipients are eventually the ones benefiting from the crime.