well, there are a bunch of issues...

one is the issue of say, pure and organic meat, properly raised and etc...

that is an entirely different thing than much of the meat in the US diet...from animals fed with anti-biotics and given growth hormone and various other practices that exposes people to a bunch of toxins...

if you are speaking ideally, of pure and organic meat...I think there are some concerns there as well, but light years less than with "regular" meat.  With meat you can easily get some digestion problems, where folks get incomplete digestion of meat, resulting in the production of fermentation in the colon...leading to the body re-absorbing some toxins.  Much of this could be avoided by having small or at least smaller portions of meat in one meal...and especially so if the meat is chewed extremely thoroughly.

Gandhi had a saying - "you should drink your food and chew your drink."  - I think that is the direct quote.  It is a kind of macrobiotic philosophy (and in various other health systems) in which very very thorough mastication makes the food so completely digestible that health is vastly improved.  I believe the macrobiotic folks chew each bite 30 times!

So, if one does all that...buy the pure and organic meat, have small portions and chew it very thoroughly...I think that 90% of the health problems of meat would go away. 

Of course, that does not engage the ethical issue around vegetarianism....which is why, I think most folks become vegetarians.