The book doesn't say that you have to give up meat or dairy. It suggests that you eat meat as a condiment rather than as a main course and try to limit your meat and dairy intake to 10% of your calories or less.
I was a big meat eater. I decided to try to giving up meat and dairy and really liked how I felt after a few weeks. I don't think having meat now and then is a big deal. I do think that dairy is pretty unhealthy and that we are not really designed to digest dairy and that a lot of people I know who have given up dairy are surprised at how good they feel later.
It is true that in cultures where few of the regular caloric intake comes from meat and dairy their incidence of disease is lower. I won't go into all the statistics on these sort of things at this point.
Of course how you eat is your "diet" - was trying to make the point that its not a diet that you go on just to lose weight - its a lifestyle change.