Olive oil gets bitter in blender?
Well, this is a common confusion between "sour" and "bitter".

The better your olive oil is, the lower its acid value - extra virgin olive oil has the lowest acid value, it is pressed in ways that reduce contact with atmospheric oxygen. Contact with oxygen increases the acid value of olive oil.

Whizzing olive oil in a blender aerates it, and the resultant oxidation increases the acid value, ie it gets more acidic and tastes "sourer".

Lots of people can discern the change, but they don't use the right word to express it ...