Lyrik had seen the Navy men wielding those things enough to know that the thing in Harlock's hand was potentially harmful, so seeing it aimed at him even briefly is enough to make him jump.

     "Gah! H-hey, watch where you aim that, sir..!" he sputters. "Wait, loose? Aah, again? Wh-what are you going to do with it?" It surely can't be anything good if he's holding a gun!