Yes, ironically enough it was a blue sticker. They had also made sure that the part you noticed was the "War Never Solved Anything" piece. Being the open-minded person that I am I did stop to think about that proposition. Was it true that war had done something categorically positive? Let's think...Except for ending slavery, fascism, nazism, and communism
WAR NEVER SOLVED ANYTHING!
In my opinion the new laws put in effect by the legislature and president ended legal slavery in America. The war part came in when part of a sovereign nation rose up and attempted to assert independence. And any Southerner worth his salt will tell you that it was about "State's Rights" and a heck of a lot more than slavery. So, no, war did not end slavery. It was necessary to protect the sovereignity of the United States... and one of the issues on the table was slavery. Furthermore, slavery on an international scale has not ended. Perhaps someone will declare war on it soon.
NAZISM, FASCISM, & COMMUNISM
Ideologies are notoriously difficult to kill, regardless of how much violence you use against them. The virtue of being an idea instead of an individual, I suppose. Meanwhile I propose that our bumper sticker owner call up all of the fascist and communist leaders in the world, plus all of the followers of the nazi ideology, and remind them that their ideology is straight out because we've already waged a war and defeated those ideas. When questioned on the basis for that belief I recommend that he yell, "You're stupid!" and hang up quickly.
In closing, the underlying truth that the bumper sticker is hinting at, but is trying to build an unstable tower on the basis of, is that sometimes there are things worth fighting for in this life. It's true on everything from a personal to an international level. But what is overlooked in his bumper philosophy, and also true on the micro and macro level, is that there are always costs associated which should be wisely weighed and that no victory is absolute - especially when dealing with isms.