Though I can’tr stand Greenwald, and am no fan of Snowden, I actually think Greenwald has a point with regards to this particular article. Everyone really is simply believing some anonymous British government/MI6 people - without question. Many aspects in the article are laughably incorrect, some very obvious lies.
I think those who choose to believe this article, want to believe it, and choose not to question it because of that.
The article is for the willfully gullible.