Actually, there's plenty of information to inform such a decision:

While the other students were allowed to leave, Ajjawi alleges an immigration officer continued to question him about his religion and religious practices in Lebanon.

So it looks like they deported him because, first, he was a raghead...

“After the 5 hours ended, she called me into a room , and she started screaming at me. She said that she found people posting political points of view that oppose the US on my friend[s] list.”

and second because he has friends (or random associates) who disagree with U.S. foreign policy.