Grad students aren't a big voting block so it's easy to stick them with the bill. It's not like they're the elderly or Iowa corn growers who can suck at the public teat and soak up enormous amounts of taxpayer money without feeling guilty about it ("Keep Government out of Medicare").
Not sure that this is a simple left versus right issue and it's really time for Americans to stop framing most issues that way. America used to lead the world in college graduates. Not any more. College tuition rates have skyrocketed because universities keep adding administrators and staff to serve themselves and students (professor salaries have actually flatlined). It's getting more expensive for ordinary Americans to attend school which leads to more borrowing and debt that probably delays marriage, childbearing, etc. And student loans are not dischargeable in bankruptcy unlike just about any other debt thanks to a bankruptcy law passed under the Bush administration that favored the credit industry.
The middle class is in decline and I doubt that this rule will help. It easy to say that one group should not expect a government handout, and perhaps grad students should pay higher interest rates and fees. But, we have serious structural issues with our economy that don't neatly fit the left/right template. And, sadly, capitalism is in decline in this country. Afterall, why did Goldman Sachs (affiliates, employees, PACs) give Obama almost $1 million for his presidential campaign? GE was a big Obama supporter as well. They want political influence and favorable legislation--remind me how much GE has paid in taxes lately and GS recently had record profits and handed out record bonus. No recession for them.
This country is run by special interests who fund most federal political campaigns. Big business supports the free market about as much as big labor. Why pay attention to graduate students when they aren't an important political block.
Finally, I suppose it's true, as one poster implied, we no longer need as many Ph.D.'s in the humanities, although sadly most Americans are largely ignorant of our own history.
Cheers.