However, if we have irrefutable evidence that the foreign official in question is a direct threat to our national security or that of our allies, then we are duty bound to take the appropriate measures to defend ourselves and/or our allies. In the case of General Noriega, we captured him, took him into custody, brought him to the United States & tried & convicted him on drug trafficking, money laundering & racketeering charges in April of 1992. He was sentenced to 40 years in federal prison. That is how we should handle removing from power the leader of a foreign country who is a direct threat to the USA. If President Hugo Chavez is a threat of the same magnitude as Noreiga was, & I think that is what Rev. Robertson was implying, then he should have said something to that effect, not advocating that we take him out.
This is a link to a CIA report regarding the assassination of Chilean President Salvador Allende & all the other activities surrounding it. This was not a proud time in American history & led to the regulations outlawing our government assassinating foreign leaders.
http://www.cia.gov/cia/reports/chile/#14