Blanche was surprised by the attack but upon seeing they were fomors he didn't know exactly which stance to take. He actually had never fought with another fomor before in Peaca unless you counted the time when Ghast tried to take off his helmet. That unfortunate Ghoul had a beating coming to him. He always figured he'd have no loyalties if a situation presented himself where he had to fight a fomor but he found that he was surprisingly bias.
Besides, what would Shriek say if he found out he was helping a group of Humans take down some fomors?
yes i'm a sexy free and single ಠ_ಠ