Yep. He sure doesn't say anything about anyone else's appearance. How about Scottie's looks, or his sorry sunglasses routine. How about Bo's hair flying all over (gross) Why pick on Carrie? I thought she looked very appropriate for the song she sang. Donna Summer style hair and an over the top disco dress.
Simon may realize (like me) that Carrie has the most potential of the group and is trying to prepare her for "American Idol" status. He treated Clay the same way, IIRC.