You can argue that graduate students and universities are just another special interest lobbying the government for a tax exemption that benefits them. There is nothing special about graduate education when you're conferring something that's inherently valuable (namely MS and PhD degrees) to a lucky few.
You could further argue that it's unfair to ask blue-collar workers in fly-over states to pay higher taxes because of the impact of such a subsidy.
There is a lot to like in the tax bill: interest on second homes isn't going to be subsidized nor are new mortgage interest on homes over $1M. Frankly, I think it should have been applied to ALL homes over $1M since many economists have argued vociferously that such an exemption is a huge subsidy to the high-cost states.
I'd also like to see a revisitation of the taxation of carried-interest for hedge funds. There is no reason to consider performance bonuses as a return on capital if they don't have any basis in the investment/capital at risk.
But arguing that graduate students (LUCKY graduate students) are worthy of some kind of exemption is just lobbying. You could easily make the same argument for active-duty armed service members. Frankly, I'd support a tax reduction on those people. They've suffered from our national follies to a disproportionate degree.