I'm going to protect Labrys-senpai. If she can fight in the battle, I will to.
And as to fight the sin of Vanity... It's ego is its weakness. Don't feed the ego. Don't make it feel important. Attack its heart... If you are not participating, ignore the conflict. Narcissus in mythology was fueled by attention... Much like a bratty child. If you do not amuse it and give it self satisfaction, it loses its power. It's basically an internet troll.