It is a question of whom you are attracted to, not what you choose to do about it. The attraction (sexxual orientation) is not a choice even though the behavior is.
The reason the behavior is no longer criminal is that it doesn't harm any other person. Neither does polygamy, for that matter, as long as the multiple spouses are consenting adults. (Notice that the law just considers it adultery, so polygamy isn't prosecuted unless there's an underage "wife.")
Pedophila, on the other hand, is harmful to children, who are not allowed to give legal consent. And bestiality is abuse of animals, which is also criminal.