Fairly true. However farmers are generally not morons so they feed the crappiest food to the animals, plus a lot of the food parts we don't eat, like what's left after you take all the kernels off of corn.
Avoiding meat altogether is probably not necessary or even that great of an idea but the American diet has much too much meat in it. We would definitely be healthier if we were more careful and cut the meat intake way down.
But then again we'd be much healthier if we learned how to deal with stress and developed some better impulse control in general.
"Half of the food we produce is fed to our livestock. If we stopped eating meat and instead used our entire food production on human consumption we could feed the entire world."
Sorta true, about half our total cereal production goes to feed livestock. And even with that we would still have enough to feed everybody in the world at least 2000 calories a day. (we grow about 14 quadrillion calories of food a year if I remember correctly). The amount of food isn't really the problem, the problems are waste, transportation, access, and storage. We do waste a lot of food in wealthier countries, and what we don't waste usually spoils because no body buys it, and the surplus helps keep food prices artificially low. In developing nations food often spoils because they lack the proper facilities to store it, and/or the transportation to get it where it's needed. Then of course there is the matter of access, even if we could get it where it needs to go, how would the ultra poor pay for it? Unfortunately we live in a largely capitalist society, people rarely do something for nothing.
Beyond recent history the majority of food people ate was not meat. I am willing to bet that the average person maybe ate 1 piece of meat every week. The only reason meat is the rule today is because of our intelligence and abilities to problem solve and produce things through the rules of nature. If we went to the lengths of creating a genetically enhanced food by changing DNA. We are still working with in the limits of nature. There is still lots of room to grow and we just need to be comfortable with the next steps and define what is morally right and wrong.