The problem with Vegans isn't that it's a diet, it's that it's a religion. You can't argue with people in a religion and they all have to try and convert you.

BTW, the following is from http://www.fathead-movie.com/

If you saw Super Size Me, you know Morgan Spurlock’s girlfriend at the time (later wife, later ex-wife) fed him a “purifying” vegan diet after his all-McDonald’s diet. (And it took him six months to lose 20 pounds on that diet.) She was known as a vegan chef for many years.
Now she’s had her own Lierre Keith moment and declared that she’s no longer a vegan. From her blog:

I thought many of the world’s problems could be solved if more people ate this way. We could end hunger if we fed grain to people instead of cattle. We could end global warming if we reduced the fertilizer, trucking and refrigeration required to produce meat. We could end the obesity epidemic.
What I ate aligned with what I believed. And that was that. But then, a few years ago, something began to shift.
My body started craving the “bad” stuff. Namely, meat.
It used to be that, when a friend ordered a burger out at dinner, I was slightly (though quietly) disgusted. But I started noticing a different reaction.
Instead of disgust, I started to salivate.
The impulse to order salmon instead of salad with tofu at my favorite restaurant was overwhelming. And, for me as a vegan, it was confusing, too.
At first, I thought: “I must be mineral deficient. Or maybe I need more concentrated protein. I’ll eat more sea vegetables. I’ll just add more nuts and hemp seeds and drink more green juice. Then the cravings will stop.”
I denied these cravings and tried to “talk my body out of them”.

It’s this part of her post that was bound to rile up the vegan zealots:

I began to see my cravings for animal foods from a different angle. It wasn’t immoral or wrong. It just was.
In fact, I came to believe that trusting your body, living your truth, whether it be vegan, part-time vegan, flexitarian or carnivore is all inherently good.

The reaction from the vegan zealots was predictable: she wasn’t it doing it right, ya see. (Really? A vegan advocate, chef and author wasn’t doing it right?)

Or my favorite: she was never really a vegan, ya see.

One of the books Jamieson wrote was Vegan Cooking For Dummies. Given the reaction to her announcement, I’d say that title was more appropriate than she imagined at the time.