>>11385685He's not wrong. If you have intestinal problems the first thing your GI doc does is move you to a low residue (low fiber) diet.
The idea behind fiber as a good thing is similar to how a coarse tooth brush is considered a good thing sometimes i.e. it's hoped to help move out junk but if it does this it's at the cost of being harsher on the surfaces its applied to.
Also there's surprisingly very little evidence it does this in the first place.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3435786/>Whilst it is often stated in physiology textbooks that bulking agents improve peristalsis, there is no proof of this in practice nor experimentally. Regardless of the food ingested, small intestinal and right mid colonic contents are fluid and all ingestible dietary fiber is suspended therein. Dietary fiber, therefore, cannot act as solid boluses for the initiation of peristalsis. In fact, dietary fiber had been shown to retard peristalsis and hold up gaseous expulsion in human experiments[22].>Dietary fiber is also associated with increased bloatedness and abdominal discomfort[22]. Insoluble fiber was reported to worsen the clinical outcome of abdominal pain and constipation[18-20]. In our recent study, patients who followed a diet with no or less dietary fiber intake showed a significant improvement, not just in their constipation, but also in their bloatedness. Patients who completely stopped consuming dietary fiber no longer suffered from abdominal bloatedness and pain. These symptoms are caused by the fermentation of dietary fiber by colonic bacteria, which produces hydrogen, carbon dioxide and methane[23]. Gases that are trapped by peristaltic colon exert pressure on the walls, causing the abdominal pain experienced by patients.>In conclusion, contrary to popularly held beliefs, reducing or stopping dietary fiber intake improves constipation and its associated symptoms. 
