Basic Economic Fallacy Alert!
People make society as a whole POORER by buying things. It is what people PRODUCE that makes society richer. When people are buying stuff with money they got from welfare, then their presence in society is, in economic terms, a pure liability.
Although many illegal aliens work, they are, on the whole, a liability.
Therefore, if they were all deported, America as a whole would be instantly richer.
When you factor in crime as an economic cost of their presence, then their deportation would increase the general level of wealth even more.
It is the demand that makes the production make sense. Nobody makes doo wop kumquats because nobody is using (consuming) them. We have to have a balance between them to make an economy go. There is nothing wrong with charity qua charity to people who desire to do something good inasfar as it lies within their capability, and it may have escaped them for a time.