I agree that Kennedy is very vague in Windsor. But leaving Windsor aside, he did categorize the issue as being about moral disapproval in Lawrence:
“For many persons these are not trivial concerns but profound and deep convictions accepted as ethical and moral principles to which they aspire and which thus determine the course of their lives. These considerations do not answer the question before us, however. The issue is whether the majority may use the power of the State to enforce these views on the whole society through operation of the criminal law. Our obligation is to define the liberty of all, not to mandate our own moral code.”
Kennedy also expressly adopted the following statement originaly written by Justice Stevens in his dissent in Bowers: “the fact that the governing majority in a State has traditionally viewed a particular practice as immoral is not a sufficient reason for upholding a law prohibiting the practice.”
Lawrence overturned Bowers on exactly those grounds. Bowers held that moral disapproval was a valid basis for a law restricting liberty and the Lawrence held it was not a valid basis.
Under Lawrence bestiality laws should be unconstitutional.