What the person failed to mention, is that grains contain Beta Glucan, that can help lower your Cholesterol and apart from something called Lentinen Mushrooms, I have never heard of anything else that contains it except for supplements.
You can lower Cholesterol with Fatty Acids and plant Stanols however.
Barley also contains Flavanoid content which are anti-oxidents, which is also beneficial.
Also the author doesn't tell people what this intestinal mucous is, he just compares it to some sort of mucous prevelant in IBD sufferers, but that doesn't mean it is, so he is vilifying a human secretion that might be beneficial to people.
I cannot say, as I don't know what this muscous actually is.
Also the Author doesn't elude to the fact, Lectins have shown medical promise in relation to Cancers and are not entirely bad.Lectin Website
The argument is however compelling and certainly for people with IBD, IBS or bloating, grains are best avoided, but in my case I'll consider them not much of an issue and continue to eat them