I may be opening a can of worms here but...

[Bulworthyproject]

I would say that wild meat is the most ethical meat option. Following that decently reared animals, but unless you go to see the farm it is difficult to judge that. I am a meat eater (I wouldn't say carnivore as I eat vegetables too) but a couple of days of veggie meals and a couple of days of fish isn't any great hardship.