Even with the drunken haze, Cor can feel his hackles slowly rising at those words. The idea of Clarus doubting someone who's more than proven his loyalty to Noct in the Marshal's eyes...it makes him want to punch something, or someone.

Definitely not Prompto, though. He's a good guy. No, a good kid.

"You are his friend, and don't let anyone tell you otherwise. Not even that ass Clarus. Why the hell is he giving you grief?"