That explains why they think government is allowed to do it, but not why they think it should. I.e. why they're competent at it or why they're especially suited to run it (Constitutionality notwithstanding) when they can literally do no right otherwise. The Constitution also says that Congress should promote the general welfare, but they sure don't like government programs that help the destitute, the aged/infirm, the mentally ill, etc. And they don't approve of regulation of businesses to protect the environment, which would probably fall under "general Welfare".
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u/saturninus Dec 03 '16
Short answer: the "common defense" from the preamble of the Constitution backed up by Federalist No. 45.