Fiber

In Dr. Lustig's talk from http://www.youtube.com/watch?v=dBnniua6-oM , he suggests that people eat between 100 and 300 grams of fiber per day, where the average American eats less than 25 grams per day. He also suggests that smoothies grind the fiber too much to be used well. I had found that suggestion odd since so many "experts" recommend juicing and smoothies to increase one's fruit and vegetable intake. Not juicing made sense to me because the "pulp" was left behind and i had assumed the pulp was the majority of the fiber, both soluble and insoluble. I have been wondering why smoothies though. Everything that is placed in the blender, is in the smoothie, fiber and all right? 
I also know from courses taken and article read, fiber is important to diabetics to help control one's "sugar". 
Today i read an article from the Settle Times written by Barbara Quinn, a registered dietitian and certified diabetes educator.
http://seattletimes.com/html/health/2021755721_healthgutxml.html
I found this quote most interesting. 
"Here’s one way it may work: Dietary fiber — the indigestible part of a plant food — travels through the body ... undigested. When it reaches the lower end of the digestive tract (the colon), it becomes food for the friendly microbes (probiotics) that live there."
What if the fiber in smoothies is ground so fine that even the insoluble fiber can be absorbed leaving very little for the good bacteria to eat? 

If you are interested in more information on fiber. This is a great place to start  http://www.vegkitchen.com/nutrition/fiber/