Probably the same way most people rationalize consuming the flesh of slaughtered animals, despite the massive negative environmental impact that has, and the better alternatives that are available.
They are not compareable imo.
Not all aspects of two things have to be similar in order for a comparison to succeed (such a comparison is of course actually impossible).
It’s not entirely clear to me how that could possibly be the case, when pasture raised animals often graze land that is completely unsuitable for agriculture. They also eat tons of byproducts of agriculture that are not suitable for human consumption.
This thing about how vegetarianism is sooooo much better for the environment is such a meme. Especially when you take into account what a tragedy modern industrial agriculture really is, with its monocrops, deforestation, and so on.
It summarises the differences in global greenhouse emissions between various types of food, and the contributions of the different sources of these emissions - farming, transport, land use change, and so on.
They cite emissions per kilogram, but that’s completely nonsensical. A kilo of meat does not equal a kilo of spinach in terms of calories or macro-/micro-nutrients.
This is a mistake that I see very often when these kinds of comparisons are made.