I think it would have been possible to make some serious arguments without the conversation devolving into a shouting match. Also, you don't know that Gemberling wouldn't have changed his mind because no one has really presented a good argument on the show.
I wish someone would have brought up what is to me the most obvious and central counter argument: animals are similar to human minors in that they are both unable to consent. If an adult has sex with a child, it is still abuse even if the child initiates the act or even if the adult claims that the child "enjoyed it." The same standards hold true for animals. As a society, we are advanced enough to know that children and animals do not have the mental capacity to understand the consequences and meaning of sex.