Nope. Especially as the groups do not have very clear boundaries.

Here's a respected figure explaining the sound logic of the mainstream attitude.

Even a superficial glance is sufficient to show that all the innumerable forms in which the life-urge of Nature manifests itself are subject to a fundamental law--one may call it an iron law of Nature--which compels the various species to keep within the definite limits of their own life-forms when propagating and multiplying their kind. Each animal mates only with one of its own species. The titmouse cohabits only with the titmouse, the finch with the finch, the stork with the stork, the field-mouse with the field-mouse, the house-mouse with the house-mouse, the wolf with the she-wolf, etc.

Deviations from this law take place only in exceptional circumstances. This happens especially under the compulsion of captivity, or when some other obstacle makes procreative intercourse impossible between individuals of the same species. But then Nature abhors such intercourse with all her might; and her protest is most clearly demonstrated by the fact that the hybrid is either sterile or the fecundity of its descendants is limited. In most cases hybrids and their progeny are denied the ordinary powers of resistance to disease or the natural means of defence against outer attack.

Such a dispensation of Nature is quite logical. Every crossing between two breeds which are not quite equal results in a product which holds an intermediate place between the levels of the two parents. This means that the offspring will indeed be superior to the parent which stands in the biologically lower order of being, but not so high as the higher parent. For this reason it must eventually succumb in any struggle against the higher species. Such mating contradicts the will of Nature towards the selective improvements of life in general. The favourable preliminary to this improvement is not to mate individuals of higher and lower orders of being but rather to allow the complete triumph of the higher order. The stronger must dominate and not mate with the weaker, which would signify the sacrifice of its own higher nature. Only the born weakling can look upon this principle as cruel, and if he does so it is merely because he is of a feebler nature and narrower mind; for if such a law did not direct the process of evolution then the higher development of organic life would not be conceivable at all.

This urge for the maintenance of the unmixed breed, which is a phenomenon that prevails throughout the whole of the natural world, results not only in the sharply defined outward distinction between one species and another but also in the internal similarity of characteristic qualities which are peculiar to each breed or species. The fox remains always a fox, the goose remains a goose, and the tiger will retain the character of a tiger. The only difference that can exist within the species must be in the various degrees of structural strength and active power, in the intelligence, efficiency, endurance, etc., with which the individual specimens are endowed. It would be impossible to find a fox which has a kindly and protective disposition towards geese, just as no cat exists which has a friendly disposition towards mice.

• Adolf Hitler (Mein Kampf, volume 1 chapter 11)

Bible, and bible thumping.

I don't know if animals can even experience it.

I would expect that they can. I have no reason to assume humans are unique in any single regard until shown otherwise, just as I have no reason to assume I think in a unique way amongst humans until shown otherwise.

The opposition are likely in two groups: 1) "it's against the natural order", 2) "it's non-consensual".

The old sodomy laws were in the first category, the new battles are ostensibly on the second, but I have this niggling feeling that we've been subject to a propaganda war by the first who pretend it's the second.

I think you give them FAR too much credit. They are not concerned when the animal doesn't want to train, dressup, get squeezed, and go to great efforts to remove sexual organs to reduce "inappropriate behaviour". There are some, very few in my experience, who are genuinely concerned about animals, and most of them are actually vegan. Do you truly think that the opposition is concerned with what an animal wants and not what we do? If so, please explain Spain where stabbing a bull repeatedly with steel spears and swords was not made illegal(also certain animal fighting dogs and cocks) but slipping it a penis was made illegal just recently?

If you wanted to hold animals up to a human standard(ie they must speak), quit changing the standard when it comes only to sex. On a personal note I am finding it pretty obvious that you've never listened to an animal, while they don't use words, they say no in no uncertain terms. If the argument is that because some humans don't listen to them, no humans should have access, then I'd love to see that applied to heterosexuals too, because rape does happen intraspecies.