I'm confused about where you the comparison doesn't fully apply. Are you refuting that there was a time that masters didn't consider their slaves inferior and treat them as animals?
No, I'm not refuting that. I think the comparison doesn't apply because it addresses a form of mistreatment of other humans, not non-human animals. Like I said, most people throughout history, for various reasons including evolutionary factors, haven't treated members of their own species the exact same way as they have members of other species. The vast majority of people don't think of fishers as mass murderers, nor do most people view abattoir workers the same way as they do executioners and serial killers. Whether this is right or wrong is a separate question from the fact that it is the case.
It's a bit unfair to make such an extreme comparison, but I don't make it a point to befriend or accompany anyone that kills any animal indiscriminately.
Why don't we start with a comparison of human and chimpanzee instead. Would you be likely to befriend someone who killed a chimpanzee today and accompany them anywhere?
We can use any non-human animal in the comparison if you prefer, although I will also point out that I wasn't referring to indiscriminate killing. We could, for example, go with a scenario where a farmer sells the meat of cattle and pigs for food; that would be the reason for killing them, so it wouldn't be indiscriminate. There are people on this very forum who have lived on farms, and most members are meat eaters. You and I still talk to them and have no problem befriending them; would we do the same with cannibalistic killers?
As for your question, no, I wouldn't be likely to befriend or accompany such a person anywhere. However, I think cultural and societal norms partially come into play here: neither your society nor mine considers it normal to kill chimpanzees for food, and they're not commonly farmed for that purpose. The same goes for dogs and cats, and if I met someone who had just eaten a dog or a cat, I would be uncomfortable hanging out with them. In addition, chimpanzees are extremely intelligent and highly capable of experiencing suffering, so that's another factor I would consider.
I recognize that being used to the normalization of eating cows and pigs but not dogs or cats is a largely subjective and culturally dependent inclination, though. Pigs are similarly intelligent as dogs, but I would have no problem hanging out with someone who regularly ate pork—and again, I'm sure that both you and I regularly talk to people who eat it. Squids and octopi are immensely intelligent, but I don't feel the same way about seeing them being eaten as I would seeing a dog or a cat being eaten. Is there a strictly objective, rigorously logical argument for this variation in reactions to the eating of different animals? I don't think so, myself, just as I don't think that there's a strictly objective reason to view farming of pigs for food as different from farming cats or dogs for the same purpose.
Again, an extreme comparison, but I suppose I should appreciate your not using the fly again as an example. I'll just point out that we've made laws against killing chimpanzees. We've also made laws about puppy mills.
By saying that the comparison is extreme in the case of a fly or a fish but not in the case of a chimpanzee, does this imply that we're distinguishing between three non-human species even if they're all conscious? Yes, the laws against killing chimpanzees are stricter than the laws against killing a fish, and the laws against killing humans are stricter than the laws against both. As far as I can see, this means that society has effectively decided to rank different species in terms of protection.
The laws against puppy mills seem to me a case in point about what I just said regarding pig farms: why are there no laws against farming pigs even though they're similarly intelligent as dogs? And if we say, "Yes, there should be laws against farming pigs too," why stop there and not also include fish, bees, birds, and other animals?
When society distinguishes between different species in terms of legal protection, it has already decided to rank them in some way. What is the baseline or threshold of intelligence or capacity for suffering that should give an animal more protection than another?
I don't have any definitive answer to these questions; I think a lot of them significantly vary based on cultural, societal, and legal norms. I'm strongly in favor of laws against indiscriminate killing of any animal, and I'm strongly in favor of laws against farming chimpanzees, dogs, cats, and various other animals for food. If you asked me whether I felt, on an emotional level, the same way about someone who farmed cattle for food as I did someone who farmed dogs or cats, I would say no. Why? I have no objective basis for that; I mainly do because of having been immersed in the norms of most societies around the world, including my own.
I also think the capacity for experiencing suffering, which evidence indicates may be related to the constitution of different animals' nervous systems, is part of the equation, which is part of why I believe it is appropriate to have stronger legal consequences for harming a chimpanzee than for harming a fly or a scorpion. Even if everyone went vegan today, humans would still need to kill or otherwise harm members of some species, whether directly or indirectly, in order to farm our crops (mainly but not exclusively insects). In effect, veganism becomes a choice between two forms of killing where one is deemed less harmful or conducive to suffering than the other, not between killing and not.
I'll just point out here now that I'm not expecting everyone to adopt my mindset straight away, but I do take exception to it being said that it's not realistic for meat eating to disappear anytime soon. To me, it's just making an excuse for things not to change because it's just what people do, and we can't expect people to inconvenience themselves. Such attitudes delay or hinder any change. I go back to my previous post and the slavery example. The problem is complacency.
There are millions of people around the world whose main form of sustenance is meat, out of necessity rather than mere convenience, and many others whose livelihood relies on fishing, animal farming, etc. While I don't doubt that complacency is part of the issue for many people, I don't think that applies to everyone.
I see it as unrealistic to expect meat eating to disappear anytime soon because 1) it has been part of humans' diets for about as long as we have existed, and entire societal and cultural norms are built around it, and 2) like I said, for various reasons that include evolutionary factors, most humans don't view fellow humans the exact same way as they do members of other species.
Is this an ideal status quo? I don't think so, since I believe that even if humans don't stop eating meat altogether, we need to consume less of it for the sake of the environment and the animals that are mistreated in industrial farms. Regardless of my belief that this status quo is not ideal, though, I think meat eating will most likely remain widespread for decades if not centuries to come. I think any major changes will probably be in the extent to which meat eating is common and in the methods used to produce meat, but the practice itself won't disappear.
