I agree. I think killing a non-human animal is a lot less than murder, but still probably / possibly bad.

I see no reason to make animals suffer, either from poor living conditions or from the method of their execution. If we raised animals in pleasant conditions and killed them painlessly, I would be hard pressed to object on the grounds of suffering to their death, except for possibly the most intelligent / seemingly self-aware animals. Of course, since we don't raise animals like that, I have earlier objections.

As far as suffering goes, I rate the suffering of pigs > sheep > cows > chickens >> fish >> arthropods. The very miserable living conditions of pigs upsets me, but I don't plan to dedicate my life to effecting change in that area. Many primates and cetaceans are far enough up the list that I would actively try to stop someone who was killing them. I realize that both are killed for food, and it upsets me, but human suffering is more important to me, and I think I can be more effective at stopping it.