Venezuela instead of Iran?

2007.11.30: Greens, citing revealed memo, urge Bush to cancel CIA plans to interfere in Venezuelan referendum and destabilize the Chavez government

Green Party leaders called on President Bush to cancel an order directing the CIA to interfere with a December 2 voters' referendum in Venezuela and to cease actions intended to destabilize the Chavez government.
The Venezuelan government uncovered an alleged confidential memo on November 26 from US embassy official Michael Middleton Steere to the CIA director Michael Hayden which reveals clandestine operations to influence the referendum and to coordinate a military overthrow of the elected Chavez government. The referendum will measure public approval for constitutional amendments proposed by Chavez and the National Assembly; polls show 60% support for the amendments.

How can an overthrow of a sovereign government bye justified? How can this memo not be front page news?