MAKING COMMUNITY COLLEGE ‘FREE’ will harm serious students, not to mention the unserious ones.

I think that's right. And I think proof can be found in the decline of 4-year colleges and universities. Here's a recent example from an almost-free education:

With freely-granted student loans to almost anyone who can fill out the application, even 4-year institutions have filled with unqualified, unmotivated students who hang around for a few years, then leave still uneducated, still unqualified, and with a debt load that's for all practical purposes unpayable.

Here's the nut graf: "There is nothing like spending one’s own money to force people to take the coursework seriously.”