drink your own bathwater 

v. A metaphor for a person or a group of people believing their own lies and propaganda. The effects of doing this can be comical, e.g., Baghdad Bob, but this is usually the harbinger of the demise of the practitioner(s).

When Mikhail Gorbachev instituted Perestroika and Glasnost, it was obvious that the leadership of the Soviet Union was having a big session of "drink your own bathwater," assuming that Communism was actually about helping workers. Glasnost exposed the average Russian to the lies they had been told, particularly about how awful their standard-of-living was as compared to the West. Subsequently, Gorbachev and the Soviet Union lasted only six years.

drink your own bathwater by Dan Weyandt March 27, 2013