It’s important to note that perfectly acceptable definitions of “abominable” include “corrupt” and “abhorrent” and “disgusting”, etc. If we hold certain things to be central to our liberties and responsibilities and theological foundations, then anything that abridges or alters or violates those standards will be within the bounds of “high level abomination”.
Also, if the result of sin should be considered in allocating a level of abomination, the potential wreckage of family life (that can be seen throughout our modern society) also argues for placing sexual sin high on the list of abominations.
One more thing: A command should not be judged by the most benign breaking of it. Two teenagers making out in the backseat of a car without the girl getting pregnant can’t be the basis for the discussion. The objectification of women through pornography and the dehumanizing effects of prostitution are a much better judgment standard - which is more in line with rape and child molestation (and the actual scriptural account in question). Just as the Word of Wisdom should be judged more by the drunk who beats his wife and children and keeps them in poverty than the occasional social drinker, the Law of Chastity should not be judged primarily by teenagers in a car.