Is there anything you can't use the Welfare clause to justify? Wouldn't it be worthwhile to give some thought to what the founders intended when they wrote that phrase. It's not a blank check. Amendments 9 and 10 still apply.
As noted above, the Founders disagreed as to the scope of that phrase. Madison favored a more restrictive view, Hamilton a broader view. The meaning is open to interpretation, in other words: even among the Founders themselves.
It took the USSC 150 years to decide that it was within Congress' discretion to define the true scope of the phrase (for good or ill).
In reality, we see those sorts of Constitutional fudges pretty much everywhere. For example, the Constitution didn't authorize Congress to allocate money for the purchase of territory from other governments such as the Louisiana Purchase. "Jefferson argued that a constitutional amendment was needed. He wrote in 1803, 'The General Government has no powers but such as the Constitution gives it… it has not given it power of holding foreign territory, and still less of incorporating it into the Union. An amendment of the Constitution seems necessary for this.'” But the purchase went ahead regardless of its apparent unconstitutionality.
Even those things which seem unarguably within the proper realm of government fall into this apparent grey area. For example, even the libertarians argue that levying taxes for the purpose of building and maintaining roads is within the proper scope of government action, but the Constitution itself refers only to "post roads," which were specific roads that connected post offices. Most roads -- then and now -- do not fit that definition. On the other hand, nearly everyone uses and depends on roads, and there is general acceptance that the government has legitimate interest in their maintenance. It seems to me that the best defense of the practice is to invoke "general welfare."
And so with health care. One can make the argument that ensuring some level of health care to those who cannot otherwise afford it, is a legitimate concern of the government, in the form of promoting the general welfare. The counter-argument is that charities could do the same, though I have serious doubts as to whether they actually could afford to do so, considering the sorts of costs Kudlow is talking about.