Simply because it is illegally located on occupied Palestinian lands slated for a future Palestinian state. The Palestinians will never agree to the existance of Ariel as a "major population center", and there is no reason for them to. Israel built the settlement - let Israel deal with the consequences. On a practical note, perhaps the future of Ariel is not so bleak after all. Just like Israel has Arab towns in it, so may Palestine one day have a Jewish town in its midst, provided, of course, that the inhabitants adhere to and respect Palestinian sovreignty and rule.
Boko Haram extremists kill 26, including children (AP)
from the article: Boycott Ariel college