First off, it's probably higher than 3%, I found estimates of 4% in an ARS study. Also, if beef is a full 1/3 of our agricultural emissions (9-10% overall), then that's a massive amount so a few people can have their cherished foods, at everyone else's expense (tragedy of the commons here).
Second, beef is proportionally MUCH worse than all other foods: we can't afford to leave a full 1/25th of our emissions on the table.
Third, you're ignoring land use, land degradation, water use, and negative health effects of beef production and consumption. To look solely at "US emissions" in a narrowly defined way misses many of the harms of beef.
Fourth, cows are mammalian species who endure great suffering and misery so that your mere 3% of emissions can lead to a relatively smaller number of calories consumed. Is it worth it to cause suffering on a mass scale for the least healthy, most emitting food source?
Even if all US emissions from beef stopped tomorrow, it would have far less effect than the US's drop in 2020. And the drop that we saw last year is similar to what we need to continue with each year this decade. Sure, beef emissions must be dealt with, but it's a fraction of a year's decreases, it's not "huge".
When it comes to climate (the topic here), banning beef is being used by climate inactivists as a cultural wedge issue to stop climate action. Michael Mann, a vegan, has strong opinions on not harping about beef out if its true importance in the climate policy fight:
I agree that the extreme views about banning beef are counter-productive. We saw the craziness that right-wing outlets propagated with a mere DRAFT version of the Green New Deal on AOC's website...this is just an HTML document uploaded by a staffer...that led to months of mis-characterization and damage to the perception of the left's views of climate.
I still think beef is a wasteful, unethical luxury, and every bite of beef comes via great cost to the millions of species going extinct and the future devastation of coastal and island peoples.
In my view, we need to place taxes on behaviors that are bad for society. Barring that impossibility, we need to develop meat alternatives, change hearts and diets, and also reform the beef industry towards sustainability. I think ideally, we'd always have cows, but in far, far lesser numbers.
Second, beef is proportionally MUCH worse than all other foods: we can't afford to leave a full 1/25th of our emissions on the table.
Third, you're ignoring land use, land degradation, water use, and negative health effects of beef production and consumption. To look solely at "US emissions" in a narrowly defined way misses many of the harms of beef.
Fourth, cows are mammalian species who endure great suffering and misery so that your mere 3% of emissions can lead to a relatively smaller number of calories consumed. Is it worth it to cause suffering on a mass scale for the least healthy, most emitting food source?