Fighting for animal liberation and an end to speciesism
You wouldn’t smash in the head of a horse with a sledgehammer, if the horse had done you no harm, because you know that smashing its head in with a sledgehammer would be terribly bad for the horse. You aren’t the sort of person who does things that are terribly bad for another.
Cows and pigs aren’t very much different from horses. Cows and pigs have done you no harm. But as part of the process that turns cows and pigs into meat that you eat, things are done to cows and pigs that are as bad or worse for them as hitting a horse in the head with a sledgehammer would be for the horse. There’s no practical way to turn cows and pigs into the meat that you eat, in the amounts that you eat it, that doesn’t involve things much worse than hitting a horse with a sledgehammer.
If you wouldn’t hit a horse with a sledgehammer, then you ought not to pay other people to do things that are as bad or worse to cows and pigs. Therefore, you shouldn’t eat meat.