if someone is demanding thanks or praise or claiming that anyone who objects to war owes them a debt of gratitude for wars such as the one just faught ... well, I think they have a slightly warped viewpoint.
I don't know about 'demanding' it, but surely if you have a right to view war as objectionable, then those that fight them have the right to view your lack of gratitude as objectionable.
It's the beauty of the free world.