Peter Singer - the controversial Australian utilitarian philosopher of jewish origin - is best known for his 2001 article 'Heavy Petting' in a now defunct sex-focused e-zine called 'Nerve'.
Singer has been controversial all of his intellectual life in his advocacy of everything from abortion to animal rights as well as his vocal opposition to the death penalty (he is particularly noted as the doyen of animal rights/liberationist philosophy). I might add that personally - while I tend to take a situationalist view of ethics (which is similar to utilitarianism but focused on the group not the individual) - I am on the opposing side of most things that Singer argues.
Singer has been a tenured professor at Princeton University for quite some time (1998 to be precise) (1) and has a strong record academically speaking. (2) He has also been given numerous awards such as the prestigious 'Order of Australia'. (3) This superficially impressive academic record belies Singer's extremist philosophy, which champions anything and everything - ethically and morally-speaking - as long as it gives pleasure to the individual. (4)
Singer's sole pursuit - akin to that of his fellow jewish philosopher-turned-sexologist Sigmund Freud - is pleasure and pleasure is the only thing that matters to him. This is a thoroughly irresponsible attitude to take intellectually for the simple reason that using the criterion of pleasure - which is the point of life in terms of society for those intellectually aligned with utilitarianism - means that everything and anything is no longer taboo (and all taboos which people can find pleasurable in whatever circumstance) are ipso facto irrational and should be abolished unless they can be substantiated. (5)
The problem with the argument that Singer is using is that there is no logical break to say when the logic stops and what you actually end up with - and in all credit to Singer he does realize this unlike many utilitarian thinkers - is a society where nothing is taboo and anything goes. In this world everything from having sex with dead bodies, mass-murders for pleasure and rapes are the norm, because once there are no taboos in society (be they rational or irrational) then society breaks down.
This is anarchy and when anarchy forms then warlords emerge and where warlords emerge there comes new militaristic autocracies based on oppression and violence. This is because where there is a vacuum of power then there will always be some new entity that forms to exploit this vacuum. This then leads to the re-imposition of social taboos at the point of a gun and then Singer and his cronies are back precisely where they start from: societies with 'irrational taboos' oppressing the individual. (6)
This problem is simply forgotten by many commentators on Singer's bestiality advocacy who either don't believe Singer's argument should be answered (as it doesn't need to be in their thought) or Singer is focusing on the wrong 'taboo' and that the rape and killing of animals by the food industry is far more important. (7)
However Singer's argument can be reduced to the nonsense that it is simply enough (I would argue the bestiality taboo is rational from a group perspective not an individual one, which is related to the so-called 'yuck factor') (8) and incidentally Singer typically ignores the thorny issue of consent (which is important in relation to Singer's use of relativistic ethics) which reduces his argument once again to ashes (as animals cannot accept or refuse as they have no defined medium to do so). (9)
Singer has since the publication of 'Heavy Petting' been on the defensive about his views on bestiality and has been downplaying them to his erstwhile friends - the animal 'liberation' crowd - as being an attempt provoke thought/discussion about 'irrational taboos'. (10) He has also suggested (11) that what he wrote 'was only a book review': however - as has been noted by others - (12) book reviews are often a safe medium for individuals to broach unsavoury or anti-social ideas to an audience in order to see how they react and if they react negatively then the reviewer can merely blame the book or suggest - as Singer has done -that he was trying to 'stimulate debate'.
This combined with the fact that Singer really does believe that the taboo against bestiality is irrational must per force mean that Singer wants to remove that taboo (as otherwise why write about it in such terms?), which in turn means that Singer wants to legalize and normalize bestiality itself.
Fortunately however we haven't come that far down the pink and fluffy brigade's road to a police state yet for that to actually occur and opposition to Singer's attempt to 'provoke discussion' was strong.
Singer must have been surprised at some of the robust responses he received - with a slew of philosophers attacking his 'philosophy' for effectively advocating the legalization of bestiality - with Gary Francione of Rutgers University leading the charge by demanding Singer immediately resign from the Presidency of the Great Ape Project. Since the views advocated by Singer meant that he was quite alright with people having sex with apes (whom couldn't consent) and thus meant that he was betraying the whole point of the Great Ape Project. (13)
Singer evidently didn't think out that consequence of his argument: now did he?
Unfortunately that initiative has not born fruit as Singer is still very much 'in place' the Great Ape Project as of this writing. (14) This is probably because Singer had only written the one small article (although he sent up another trial balloon advocating the legalization of bestiality in November 2023) (15) and had received such a ferocious public response to his advocacy that he shied away from being too explicit going forward: thus it was in Singer's sponsors (such as Princeton) interests to draw a line under the matter and say no more about it as long as Singer didn't court too much public controversy on the subject again.
That said the fact that Singer - as a known academic proponent of bestiality (as while he doesn't superficially appear to be doing so: his philosophy still requires that he supports its legalization and normalization) - still remains in place and thus allows him to champion it - directly or indirectly - to his students at Princeton and thus pave the way to that which he desires: a society which thinks it is normal for individuals to have sex with non-human animals.
References
(1) http://www.villagevoice.com/2001-03-27/nyc-life/you-re-an-animal/
(2) http://www.life.org.nz/bioethics/bioethics1/
(3) http://www.thepunch.com.au/articles/peter-singer-doesnt-deserve-an-order-of-australia/
(4) http://www.yale.edu/yfp/archives/01_05_singer.html
(5) Cf. Neil Levy, 2003, 'What (if Anything) is Wrong with Bestiality?', Journal of Social Philosophy, Vol. 34, No. 3, pp. 444-449
(6) A similar point; although phrased very differently, is implicitly made by Piers Beirne, 2001, 'Peter Singer's "Heavy Petting" and the Politics of Animal Sexual Assault', Critical Criminology, Vol. 10, No. 1, pp. 43-55
(7) http://www.upc-online.org/010422bestiality.html
(8) Gordon Preece, 2002, 'The Unthinkable & Unlivable Singer', pp. 23-25 in Gordon Preece (Ed.), 2002, 'Rethinking Peter Singer: A Christian Critique', 1 Edition, Inter-Varsity: Downers Grove
(9) http://www.thephilosophytakeaway.com/2012/10/peter-singer-by-samuel-poole.html
(10) http://www.animalliberationfront.com/ALFront/Interviews/Interview%20with%20Peter%20Singer.htm
(11) Ibid.
(12) http://www.princeton.edu/paw/web_exclusives/more/more_letters/letters_psinger.html
(13) http://www.euthanasia.com/singersmith.html
(14) http://www.projetogap.org.br/en/historic-meeting-2013/
(15) https://www.dailymail.co.uk/news/article-12738695/Princeton-professor-Peter-Singer-article-promoting-bestiality.html; https://www.foxnews.com/politics/princeton-professor-animal-rights-activist-called-bestiality-thought-provoking