Butters is always the slightly clueless underdog because that's what makes us root for him, whether it was his numerous near-death experiences in Butters' Very Own Episode or his being mistaken for a stray dog in the season primere. With him now causing Cartman all the grief, he only becomes annoying. The only thing that could have made this episode worse was if Butters was actually knew it was Cartman disguised as AWESOME-O the entire time, though thankfully that didn't happen, which keeps this disaster from reaching the level of Wing or Christmas Classics.
Personally, after this episode I'm surprised Cartman never pulled another Scott Tenorman on the little blonde kid. After all, Scott put Cartman through far less and humiliated him on a far smaller scale and we all know what happened there. It's amazing Butters is still breathing to this day.