Environmentally grass fed cattle is even worse, due to land and resources and deforestation, though technically it's supposed to be more "humane" the cattle are still slaughtered and artificially inseminated.
Also you're wise to spot the sugar fallacy, most isolated studies I have observed claiming any kind of meat eating is more sustainable than veganism, contains some stupid mitigating factor, like actually only testing sugar, or comparing raw meat to lettuce, instead of cooked meat to soy or beans.
I've actually read in my science text books a simple math problem that shows environmental impact of ANY animal products compared to vegan meals. Even 200 calories of animal products increases a 2000 calorie diet up to 3800 calories of environmental impact.
As for cruelty, unfortunately there's no way to completely eradicate harm to field mice or insects in agriculture but it does far less harm than animal agriculture.
I have even read compelling arguments about palm oil complaints being a red herring, since it keeps people from going vegan, is a single issue speciesist complaint, actually tends to use land that was already deforested for narcotics or animal agriculture, and since palm oil is so high yielding and can't completely be stopped, campaigns to force palm oil to be sustainable actually do less harm to animals and the environment than blindly boycotting it.
"Thinkers may prepare revolutions, but bandits must carry them out"~