Gabriel knew his talent, so he didn't mind this ignorant mocking. Not as if he was really a student here. He was only here for six more days on his mission.
He knew that everyone was going to know what he truly was as soon as he was going to succeed in his mission. That was when the world was going to know about the appearance of a Death Mage.
There was no need to offend too many people for now since the more he offended them, the more they were going to be on his tail which could make it hard for him to shake them off and execute his tasks, for which he needed absolute freedom.
Fortunately, it didn't take long for Lishen to intervene, stopping Ray. "Enough. Talent isn't everything. Even people with talent can fail, and even those without talent can go on to become great mages. So you shouldn't judge. Talent is just one factor in the grand scheme of things."