I eat meat and try to reduce my consumption because I recognize industrial meat production is wasteful, causes needed suffering, and has a big ecological footprint.

Who cares about vegans if modern society fails apocalyptically? I'd rather work to prevent such an event and a huge part of the population would be doomed regardless of their diet. I salute those putting in the extra effort to be fully vegetarian/vegan even if I don't quite agree with some of their extremist militantism.

Our efforts would likely be better placed encouraging more people to reduce their meat consumption. It's a more realistic goal and can have a big impact.

we eat meat because we can

Truly the greatest reason anyone has had to do anything.

and well, also should.

Because we evolved to do it? Are you saying we should do every single thing we evolved to do? Let me just go shit in the woods and die in childbirth then I guess

If modern society falls I'd like to see the vegans after about a year

Gee fucking whiz, maybe the morality of an action depends on context and the available choices. Maybe doing unpleasant things to survive in an apocalypse is actually completely reasonable. Or maybe, just maybe, killing someone to save your own life is still bad.

If killing animals for food is evil then all cats, lions, dogs, and generally all predators are evil.

Evil is a choice. The sun isn't evil for giving people skin cancer. Volcanoes and hurricanes aren't evil. And neither are nonsapient animals that can't just choose to eat meat. If you want to be treated as the equal of a cat then go shit in sand and live off mice. Or, use your big brain to actually do something good.

If you want to realistically improve the lives of farm animals, then go for laws on better treatment while they live.

Yeah, sure. Let's start with a few simple policies to help out the animals: no milking, no forced pregnancy, no genetic engineering to make them lay eggs every day, and no killing. That should help the animals out.