[loripo]

We humans have many and varied taboos re food. Some religious, look at the things that were prohibited in the Old Testament. Some of these things, like eating pig, were actually sensible, in stopping the transmission of parasites. So it was a matter of safety and hygiene. Going back into prehistory, it must have been advisable not to try to hunt something that might actually eat you instead, but now people do eat bear, alligator for example. Herbivores were easier both to catch and to keep, as they grazed and didn’t need to have meat provided, which would have been self-defeating.
Even free range chickens eat bug and worm meat! It appears that herbivores might actually be more easily digested and taste better. Have a look at Wiki (not my first choice of site for info) but they have a good list under ‘Taboo food and drink’.
With dogs I think it is mainly that we form really close bonds with them and they do become members of the family.
I’ve eaten horse and whale (I don’t remember what they were like).