serene delusions
As noble a thought that this thread is, not everyone can become vegetarians. There are certain nutrients that many people have difficulty absorbing from alternate sources, including iron, calcium and B12.
Some of the information you've provided is rather misleading. One thing in particular is that cholesterol levels are not controls solely by your intake, but also by your genetics and activity level. Lazy vegetarians with bad genes can have cholesterol as high or higher than a meat eater, placing them at just a high a risk for heart disease.
A person's life isn't going to be magically better if they stop eating meat. The environment isn't going to bounce back simply because there are a few less cows. Where are all those cows even going to go if they're not eaten? They'd still have to be killed and used for something. Can't just leave them there, because that solves nothing.
To begin, no, not everyone can become vegetarians. As has been mentioned earlier, even just cutting back on red meat consumption can be of assistance to the environment, general welfare, et cetera. Regarding iron, calcium, and B12, if nothing else there are vitamin supplements. If they have difficulty absorbing them from the myriad non-meat sources, I can't imagine anything short of a concentrated supplement helping them out.
Granted, cholesterol DOES have a highly genetic component. However, for the vast majority of us, it IS related to intake and exercise. Cholesterol was by no means the focus of any of my arguments, so I do apologize for simply skimming over it.
Amusingly, there have been several studies showing that people that are vegetarian wind up with some amusing benefits, such as "tasting better." ;-3 Yooooou know what we mean. That's generally just because vegetarians end up eating more fruit and vegetables, which construe natural sugars that sweeten such liquids. Aaaanyway... you would benefit from looking at the sources that I cited earlier to the fellow with the brownish text book. It would demonstrate to you that, YES, the environment actually WILL have a better time if there are fewer cows. Disregarding the methane, there's the whole pasturing thing that just royally screws the environment. You also operate on the belief that even if we stop eating meat, the cows will continue to be farmed. That doesn't really make sense. Supply/demand economics would imply that, with less demand, supply would have to cut back production in order to remain competitive. It's not as if suddenly there are going to be millions of excess cows, if anything it would be a gradual process.