Distinguishing homosexuality from bestiality on an argument based on consent fails in its moral consistency unless the one putting forward such an argument is a strict vegetarian. Many of the people reading this will have just sat down to a dinner comprised in part by the flesh of a creature that was stuck in a holding cell living on cheap corn byproduct for all of its short, miserable existence before finally being relieved of its perpetual suffering by having its spine severed, killing it instantly if it's lucky. No consent, there, either. Gentle sex would, presumably, be the less objectionable of the two if the animal had any say in the matter. Further--and I'm speculating here, but reasonably, I think--there are probably pets out there, such as dogs whose reason for being is to make their owners happy, who might actually enjoy it.
The point is, opposition to bestiality, at least in the contemporary Western world, rests almost exclusively on the ick factor--probably to a greater extent, in fact, than opposition to homosexuality does.
For honest progressives who genuinely want to try empathizing with conservatives who find homosexuality disgusting and consequently morally appalling, here's a worthy thought experiment: There's a big national push to legalize and normalize sexual relations between humans and other non-human animals. Many of the animals that will become sex pets if bestiality is federally protected will be bought by bestials from slaughterhouses, thus saving their new charges from the aforementioned miserable experiences described above. Instead, the creatures will live with affectionate owners through the duration of their natural lives. Are you on board with the campaign? Would you feel some resentment if support for such normalization was all over popular entertainment and in the press, persistently insinuating that you're an evil, bigoted troglodyte if you oppose as much?
We are deeply in Haidt territory here.