Fair enough, I'll bite. What you posted is a pop science article and it aptly demonstrates what I mentioned earlier. For the sake of discussion, pop science has no peer review that's worth mentioning. Among the references are actual researches with their own goals and conclusions - these are certainly peer reviewed.
As for the article
A few excerpts.
Vegetarians generally consume as
much iron as, or slightly more than,
Said to be the concluded from . Let's see , then. The purpose of  is clearly stated in their abstract - the study of bioavailability of iron and what controls (or inhibits) absorbtion - groups of Dutch people seem to be tested.  is obviously being quoted out of context for they make no such claim.
There is no way of knowing, in general, that either one consumes more iron than the other. Rather, it is important, that either diet could provide sufficient amount of iron.
The article poses an empty statement to meet some necessary word count or some such.
Many scientists are calling for a
substantial reduction of livestock products
in the diet of humans as a major way
to reverse climate change.
Wrong. The following conclusion is arrived at in .
Consuming a more plant-based diet could to an extent alleviate the negative environmental impacts related to food production. As a method to feed ourselves more sustainably, behavioural adjustments appear to be a very important tool.
They make no certain claims, rather suggest that this is worth investigating and I agree, but this does not imply what was said in the article.
I also found this gem
In addition, beef production
generates considerably more manure
waste than from any other animal food
This is said to be , which contains political statements in its conclusion. A big nono, so we'll regard that as a tongue-in-cheek essay.
As for manure itself, it is a fertiliser Around here, that's how seasonal agriculture functions. The land is fertilised with captured manure. Live stock is as essential to plant life as it is to live stock.
So, by now I think we get the picture. It is not about which diet is 'better', rather which diets are suitable for which people. As a prevalent characteristic of many references of the article - the goals of those works are to study the effects of either diet and to find balance. As an extreme example there is a certain condition that may cause (near) paralysis for people on a daily basis. Consuming more meat products significantly alleviates the condition (this is a recent discovery by G. Pilz based on relevant theory, he recently gave a talk in our university and as he himself suffers from this near paralysis condition, he applied the theory to narrow down his diet very quickly to determine which products he should discard).
We should distinguish between veganism and veganism*. The latter is a political crusade, while the former is merely another way of life. I know people who have tried vegan diets for months only to end up more in despair and I also know people who have no problems with having only plant foods. Lots of interesting research is carried out on the subject of diets, but the crusaders are incorrectly quoting these discoveries. This is no surprise, though, while the meat eaters don't have their clips of loons with flamethrowers burning down bushes of berries, plenty of pop science has been written against vegan diets. It is not so well-known simply because it's not the stance promoted by the propaganda machine.
Don't become a crusader, please. If your diet works for you, then all is well. As long as you are honest with yourself, you shouldn't get into health trouble.
Now, I need me a lamb leg, baked potatoes, some tomato salad and lots of gravy. Have fun