My guess is this hinges on the "discriminatory" angle, but not in the way you mean. "Terrorist" is a vague term, and terror-activities are engaged in by both friends and foes, and by "lawful" (i.e., state-backed) groups on all sides, including by the US forces. (which fine, I guess, it being war and all...) But "unlawful" is limiting, in that it doesn't allow us to acknowledge and work with fringe groups such as the Syrian rebels, et al. "Unprivileged" basically means "somebody we don't like", and opens up US actions (pro and con) to a broader swath of groups. Whether that's a good or bad thing depends upon a person's philosophy.
Im guessing "Unprivileged" is also meant to let Netanyahu off the hook, since some of his bombings etc. could technically fall under the terrorism category.
OTOH, the clarity of the term "terrorism" has eroded in much the same way the term "murder" has, when you look at the catch-all "Felony Murder" has become.
Not everyone is buying into the new labels, though. The group of NATO protestors who were arrested in a Chicago sting and charged with terrorism were acquitted on that charge,
http://dissenter.firedoglake.com/2014/02/07/in-spite-of-political-prosecution-jury-acquits-nato-3-of-all-terrorism-charges/but Pennsylvania thinks it will have better luck making the term stick to Eric Frein.
