Guess what OP means is that people found the scene with the old man squicky and disgusting, but Seb/Ciel and Claude/Alois a-okay.
Well, of course people like their shota more when both of them are good-looking - and most importantly, being a shota shipper doesn't automatically mean you're into rape/sexual abuse, OP. ;)

Although Kuroshitsuji II was trolling a lot, I can see no trolling here, the series just likes to make things really effed up.