All the soldiers on the base know that you avoid physical touch, because you don't like it, and that you always retaliate with a kick or punch, as a form of defense.

You're in your corner, playing on your cell phone. When Ghost approaches and touches your shoulder to get your attention, but that's when he remembers your problem with touching. You quickly retaliate by punching him hard in the stomach. The other soldiers saw it and started laughing at the situation Ghost was in.