This is so idiotic I nearly ignored it.
The issue is consent. An animal cannot consent, nor can a child.
Again with the "consent" dodge. Yes, animals *can* consent in fact, though they may not "consent" in law.
Again, Homosexuals couldn't "consent" either prior to 1973. Did their acquisition of legal "consent" in 1973 have any significance other than as a technicality? They were doing it anyways, regardless of what the law said.
So comparisons to these are ludicrous. What is being discussed is partnerships between consenting human adults....it takes a true moron to compare that with bestiality, in which there is only one consenting human. Grow up.
If you take this "consent" tack (assuming you are referring to legal consent) you are hitching your argument to the ever changing winds of the "law" instead of something immutable, like natural law.
In other words, your argument lives and dies by what is currently "the law", rather than what is actually true or false.
Change the law, and your argument becomes false.