To describe Peak Oil as a "theory" is like describing sunset as a "theory". When something happens over and over again it is called a "phenomenon" and not a "theory".
Instead of hitting the various right and left wing blogs and editorials, one should review the historical data on production and consumption to see if you can spot any "peaks".
The British Petroleum Statistical Review is hardly a left-wing, enviro-zealot publication. Rather, it is a careful compilation of oil industry statistics put together by one of the largest companies in the business.
These data can be reviewed in a series of interactive data graphics at the Energy Export Databrowser:
Even a quick review of nations like Indonesia, Egypt, the UK, Norway, Mexico, Argentina, ... will demonstrate that peaks are a phenomenon, not a theory.