My post was done facetiously.
However, to open a can of worms, the destruction of Alderaan could be compared to the real world tradegy of August 6, 1945. A destruction so horrific, it effectively ended the war. This act was perpetuated by a nation that, by Vonpenguin and RogueCorona's definition, should be declared a terrorist state.
You really need to brush up on your history.
At the time Japan and the US were at war with eachother. The US was planning a land invasion of Japan and were expecting casualties in the hundreds of thousands. So many purple heart medels were made that we are still using the same ones printed back in the 1940s. Bombing Hiroshima AND Nagasaki (a lot of people forget the second one) gave a slim opportunity for the Japanese to surrender, a surrender that almost didn't happen.
When Alderaan was destroyed, the Empire was not at war with another sector spanning government. Alderaan was pacifistic and was no threat militarily. But it was a symbol of dissent towards the Emperor. There is no real world example of such a horrific act during peacetime except maybe the crusades. A real world hypothetical example would be the united states nuking Switzerland in 1946 because they wanted to try out their new 1000 megaton nuclear bomb, and they would use a second 1000 megaton bomb on anyone who objected to the previous action and there would be nothing anyone could do about it