He could see the differences - he knew of them, sure, but Pierce still didn't think the differences justified anything. Casper could have been tossed to the wolves, just due to that spine-tingling horror that he gave off as a baby, but no. He still was put into a loving home regardless. And now he was an adult, and thus should act accordingly - but instead he backed up Pierce's original foreboding train of thought with his behavior.
"No matter how he was raised, he's not allowed to punish people for anything," Pierce said as a matter-of-fact. "His anger cannot be released like this. You know that as well as I do. And it does have everything to do with maturity because how is he going to ask them why? With his fists? He's not ready. He can't even handle talking about his biological family, that was why he was so mad at me. Because I knew things from you already."