After the Bolshevik takeover of Russia in 1917, a single member of Britain's Cabinet, Winston Churchill, appealed for robust military intervention to crush the new regime. His colleagues weighed the costs--the loss of soldiers, international derision, revenge by Lenin--and rejected the idea.
The costs were avoided, and instead the world was subjected to the greatest man-made calamities ever. Communism itself was to claim perhaps 100 million lives, and it also gave rise to fascism and Nazism, leading to World War II. Ahmadinejad wants to be the new Lenin. Force is the only thing that can stop him.