We currently eat animals as a normal part of our diet (for most of us, including me, anyway). To do this we treat the animals horribly. Incredibly badly. And we know it.
It's very easy to see how society's morals will probably change on this, in fact are changing on this, and how in 50 years' time our current stance on eating animals could be seen as monstrously immoral and indefensible.
Animals are not moral agents, and eating them is not different from eating plants. Both are part of the biosphere that we manage to our benefit.
And there are plenty of people who would vehemently argue that eating their pet puppy is very, very, very, different from eating a plant.
Good arguments, particularly in Australia, for eating wild pigs, clean skin bulls, camels, donkeys (mainly for pet meat IMHO), etc. Kangaroos, unculled, explode in number past the sustainability of their landscape and litter the ground with bones - humans estimate a cull target and shoot to reduce populations, only eating a few themselves (leaving many on the ground for "nature").
I will say though, I would only ever consider eating a dog in a life or death situation.
If there was no absolute need for me to eat a dog then I would not do it, and even if there were it would be a difficult moral dilemma for me that should I survive could possibly haunt me for life, but for my ancestors it was a common occurrence.