You may like to think that animals that are slaughtered for food suffer as little as possible but that's really not true. Their suffering is limited to the extent that it affects the final product. Actually, not even to that extent all the time. Reportedly factory-farmed pork suffers significantly in quality because of stress to the animals.
My understanding is that it's basically possible to eat beef from cows that have lived fairly decent lives (if not full ones -- even grass-fed cattle that wander huge and beautiful ranges are killed young). The majority of cattle raised in the US eat lots of grain, don't have enough room to graze, and don't get to form normal family and social bonds, but some do (you have to look for it). Here in Wyoming you can go to meat markets that will tell you which ranch your beef comes from and where it is. In some cases you can knock on the rancher's door and get a tour. This is what people tell me, at least (I eat vegetarian). Every ranch is different, obviously, but to some degree ranching practice is still passed down through family and community ties, and many ranch owners live on their ranches and do some of the physical work (this gives the decision makers a stake in the conditions affecting workers and the local environment that just doesn't exist for the people that set many intensive agriculture practices).
It's much harder with pork. If you want to eat pork that wasn't raised in sickening conditions (for the animals, the workers in the feed operations, and the environment) you really have to look hard. You'll have to pay a lot of money for the little pork you do eat. With poultry you're SOL unless you personally know the farmer. All the bullshit greenwashing you see on packages at the supermarket is simply that: bullshit greenwashing. "Cage Free" and "Free Range", as they affect poultry raising, are basically meaningless. All the big poultry operations are major corporations that will tell you anything to sell you something.
On the other hand, beef supposedly has a very high carbon footprint and unquestionably has an enormous land-use footprint. This means that it contributes enormously to habitat destruction and the loss of native grasses (so places like Wyoming and Texas used to have far more diverse meadows than they do now). The environmental consequences of intensive agriculture generally are pretty bad. Read about manure disposal practices on poultry and hog farms. Read about streams running red with bloodworms. Read about groundwater contamination. It's plain gross, and materially affecting the rural parts of our world. Then there are monocultures, unintentional gene patent infringement, and chemical runoff coming from grain agriculture.
It's just like a lot of our other conveniences that have nasty consequences. We have to weigh whether this convenience is worth it. The car culture has its conveniences, and it has consequences that are just reaching the shores of Louisiana. The transaction between a consumer and a corporate chicken producer, or between you and a car or oil manufacturer, will usually be mutually beneficial, but has externalities. Animals suffer, the environment is damaged, in many cases people suffer, too (have you ever lived next door to a modern hog feeding operation... or even driven through Iowa on a stuffy summer day?). If we could properly measure these externalities (including risk factors for things like oil spills) we could pay them as we manufacture, building in their costs. This would create an incentive for responsible behavior. Instead the government subsidizes and bails out the people that fuck up (subsidies and environmental allowances for factory farming practices, whether meat, dairy, eggs, fish, or grains, are criminal -- and we all know who ultimately foots the bill for oil spill cleanup, bank failures, etc.). This creates an incentive for irresponsible behavior. It needs to be fixed. Even the way we measure our economy is corrupt, as if all activity is equally good; making, taking, and breaking are all counted as one. It needs to be fixed.
I'm not going to be high and mighty because I'm a vegetarian that doesn't drive much. Those are pretty tiny sacrifices, and I will admit that I act selfishly all the damn time. I certainly won't insist that you eat vegetarian -- that would be hypocrisy -- just that you understand the facts. People will usually not go far out of their way for causes as remote as native grasses in Wyoming or wildlife of the Gulf of Mexico. We just won't. Hell, we don't know how to do that when the consequences of every commercial action can be so dire. So we must radically change how we account for externalities so that they show up in the bottom line.