Red's smile left his face as the news of his absence was laid out plainly in front of him. Although he had prepared himself to accept the fact, his body still resisted accepting it. After all, Red was the type of person who's always on the frontlines of the battlefield. If that thing was taken away from him just like that, it's as if he lost all purpose in living.
Just like the majority of Resistance members, Red lived to fight and defend humanity from the relentless humanoids. And he pretty much lived all his life having that mindset and fixed choice. But now, however, that fixed choice was taken away from him and he doesn't have a choice but to take it in wholly without complaining since there was no use retaliating with a differing opinion.
