An article in the guardian is not a resoundingly strong source, particularly given how news sources like to report health topics.

If you look at any of the reviewed research by academics, it’s pretty clear it’s something they want to look at more, but it’s hardly a definitive “horrible for you” or destroying the blood brain barrier.
In one study they only let mice drink emulsified water, and then gave them a food substance they were allergic to. This resulted in an increase in diarrhea.

If you’re going to cite the guardian and “common knowledge” as your source, you might hold off on the “head in ass” accusations.