When someone read his mind it was usually harmless, but as the thoughts of other people's actions where placed into head like some vision, that's when it left a bad feeling. Truth was, he was sorry for leaving behind the few that befriended him at the school, and a part of him even felt conflicted about his switch to Magneto's side.
"You didn't have to do that," he speaks in regards to her defending him against the others.
Let them talk behind his back, people always did, they were only hurting themselves for what was yet to come, and the less he knew, the less they were from getting hurt. Magneto told him not to hurt others like them unless they were defending humans, and a part of John hoped the ones who back-talked him would someday come to the front of the line and ask to be taken care of.