Answer:
A counter-argument to the claim that the allies did not stop fascist aggression because the liberal progressives of the time underestimated the danger is that there were other factors at play. For instance, after the devastation of World War I, many countries were hesitant to engage in another costly and deadly conflict. Additionally, the Great Depression had a significant impact on many countries' economies, making it difficult to justify the costs of military intervention.
Furthermore, the rise of fascist regimes was a relatively new and unknown phenomenon, and it took time for many leaders to understand the full extent of the danger they posed. While there were certainly some who underestimated the threat of fascism, it is not accurate to suggest that this was the sole reason why the allies did not act sooner to prevent its spread.