If you take the argument to those extremes, you'll end up not eating anything. Or you'll spend your entire life trying to work out what impact your actions might have in order to justify whether to take them or not. The OP clearly stated their criteria. You also have criteria for what you choose to eat which could just as easily be picked apart with similar reductio-ad-absurdum 'reasoning'.

Not necessarily. Eating pastured-raised grass-fed meat benefits the environment by nurturing soil and sequestering carbon. So if you base your diet around pasture raised meat and local produce, you can overcome many of the downsides of industrial farming while benefitting animals and the environment at the same time.

Well... very few pastures actually store anywhere near that amount of co2. my numbers are based on evaluations of carbon sinks in northern Europe (northern germany and Scandinavia) that my wife did. the publication is in Swedish, but if anyone is interested I can dig it up. The result was that less than 10% of optimal pastures(current and potential) were effective carbon sinks.

Where do you think animal feed comes from? It takes the times more farmland to raise a cow vs making bread.

Not all meat is the same. A slice of deli bologna isn't the same as a cut of pasture-raised sirloin. One comes from a factory that requires animal feed and antibiotics, the other comes from a farm that only needs sunlight, rain, and grass.

The argument was that it destroys habitats. "Pasture raised" animals are still taking up vastly more land per calorie produced, than regular farmland. In fact they take up even more than regular factory farm, because the factory farm is optimized towards efficiency and corn is more economically efficient feed than grass. There isn't enough pastures in the world to feed everyone pasture raised meat.

This is not true at all. The majority of the land mass on Earth is grassland. At least it used to be. What are now cornfields in North America used to be plains full of bison that fed on grass. We can re-create a similar ecosystem using high-yielding methods popularized by modern grass-fed operations like Polyface Farms, and management techniques like rotational grazing.

A grassy plain supports many fewer animals than the equivalent corn field. Otherwise there would be no economic incentive to grow corn instead of raising livestock on the same land. So you would need much more land to support the same amount of animals, land we just don't have.

Prior to Europeans arriving, it's estimated there were 60 million wild buffalo in the US. There are now 93 million cows in the US. And those cows are much fatter. Bred to produce more meat, grow faster. So consume much more food (and produce more per unit), so the comparison is even worse than that.

How much protein do you get from bread, though? A calorie is not a calorie.

From 100 g of soybeans you get 36 g of protein, vs 30 g of protein from 100 g of beef.

Barring strange niche medical concerns that don't affect the vast majority of the population, humans can live healthily without any meat products.

Whether or not you personally choose to is not my concern, but the root of your argument doesn't really hold water.

Yes, but farming soybeans destroys land and is dependent on pesticides and chemicals from companies like Monsanto. Pasture-raised grass-fed beef instead revitalizes land, provides natural fertilizer for plant growth, and sequesters carbon from the atmosphere to combat climate change. Not all meat is the same.

The majority of beef raised in the US is raised on corn and soybeans.

Right. This needs to change.

I actually agree entirely, but factory farm meat will continue to be cheaper so long as corn subsidies are so high, and those aren't going anywhere any time soon. Which means that for the time being, meat consumption is the less environmentally friendly option.