Some economists would even argue that apparent evidence of irrationality should always be interpreted as a sign of hidden costs (to acquire or process information in a rational way) or model misspecification (which is responsible for the divergence between the model based fundamental price and the observed price).
According to this view, rationality of behavior is not a falsifiable hypothesis but an organizing principle of economic thinking. The conclusion of this line of thinking - which by the way I certainly do not share - would be that bubbles cannot exist by definition5.