Sexual liberation

In the era of sexual liberation, not everything is permitted. The question remains, why are some things OK and others are not? What is the underlying logic of it all?

(I can understand the traditional moral arguments against bestiality. One of the first persons executed in Plymouth Colony was convicted of taking liberties with the livestock, which strikes me as extreme, but I understand the position. However, in the new morality in which it is illegal to discriminate against people based on sexual preference, aren't bestiality laws a form of discrimination against some with a particular sexual preference? Why should the right of a goat to its virginity outweigh the rights of a pervert a person with a "special" sexual orientation or need? I do not understand the logic of the animal rights people, but it seems to me that they are a lot like the Puritans.)

The article also has a funny bit about a state legislator who did not know what animal husbandry was.