Well, to boil it down, my argument is this:
1) Yes, people have a responsibility to help others, whether it is the poor, the sick, etc. Charity is a sacred duty of all Christians.
2) By using government / laws to FORCE people to give to the poor, you take away their freedom to CHOOSE to do the right thing.
3) When you give the government the power to decide who gets what, you take away some of the peoples' freedom, you handicap innovation, and you push out private charities.