In one of aesop's fables, a fox is unable to obtain some grapes that he truly wishes to have. however, after failing to obtain them, he downplays their importance. this behavior is most consistent with the defense mechanism of

This behavior is most consistent with the defense mechanism of "rationalization".

Explanation:

Rationalization refers to a defense mechanism which includes clarifying an unacceptable behavior or feeling in a sensible way, keeping away from the genuine purposes behind that behavior. For instance, an individual who is turned down for a date may defend the circumstance by saying they were not attracted to the next individual. A student may accuse a teacher for his poor test score but in actual he has not prepared his test.