You know Padmapani, you are just focusing on the offensive part of the war.
There is nothing wrong in defending your country. Being dragged into a war is completely different than waging a war. Even I want an ideal world but I'm also a realist whose country is surrounded by 2 aggressive countries and one whose population is undergoing severe radicalism or at least a part of its population.
So once again, it comes down to the "why", we all got to do it. A solid rational non-capitalist, non-greedy reasoning should be present & defence is definitely one of them.
One question to you - Do you consider defence of a culture, defence of a religion however "different" it is, is a good enough reason?