Why are despots who are US allies called 'leaders',but elected leaders who aren't allies get called dictators?

For example, I have never once heard psychotic despots like Ali Abdullah Saleh or the Saudi or Bahraini royals described as such by the US media or government. However, 3 times democratically elected Hugo Chavez gets labelled as a dictator almost every time his name comes up. Is the definition of a dictator in the USA someone who doesn't toe the US line, regardless of how he or she entered office?