Yes, that's exactly it. Respectable people would have felt the same way about homosexuality 100 years ago as you do about sex involving minors.
Further, your characterization as "rape of a minor" is problematic. What's a minor? If one minor is involved, it automatically becomes rape? In much of Europe ages of consent are surprisingly low (14) to Americans, who tend to expect 18. What about a 17 year old and a 19 year old? Two 14 year olds? A 15 year old and a 20 year old? Is what's 100% wrong and prison-bound in the U.S. morally permissible in Spain because the laws are different?
Or maybe you have access to the Objective Moral Truths, such that this game is easy for you? If so, do share. It'd make all of this so much easier.