I thank everyone for their time and consideration on the topic. I think it's been answered strongly. In summary: once a symbol or word has been used negatively or for great harm, it is now sacrosanct, and cannot be used for anything else, nor have its meaning changed or altered, for fear of forgetting the vile things done with it.
I personally do not hold this view, but I respect the majority opinion here.
I think you miss the point. Certainly old harmful symbols can be rehabilitated and changed. However, enough time must have passed so that their resurrection is not a further attack to the traumatized survivors and those who know and love them.
You are declaring that the horror of what the swastika represents is far enough in the past for it to be used lightly. That isn't true. Horrific events last, and World War II is still within living memory.
The American Civil War, which you also brought up as an example, ended 147 years ago, but its effects, particularly the savage oppression of free blacks, were not even begun to be addressed until perhaps seventy years ago, and not lawfully put down until only forty or fifty years ago. As for holding grudges, evidence suggests that there are a not inconsiderable number of Southerners who still to this day resent losing.
Napoleon was used as a bogeyman of evil and terror for nearly a century after his heyday (consider that Conan Doyle used his name as a watchword for satanic evil in his Sherlock Holmes stories, more than seventy years after Napoleon's death).
World War II is still fresh with us. I have family members who remember those years. I knew someone who was a commander on a landing tank craft in Flotilla 6 in the Solomon Islands in 1943 (nice guy, he lent me his Charles Addams books and George Gamow's pop physics). My most beloved teacher was born in 1941, in Poland, on the run from the Nazis. My grandmother lived in Washington, DC, supervising telephone networks during the war. My grandfather set up air bases.
And although not all those people are still with us, I remember them, and what happened to them. And there are thousands and thousands more people who lived through World War II, or know and love people who lived through it.
Maybe in another couple of generations someone might be able to resurrect the old Nazi symbol without offending people. Maybe not.
But now? Oh, don't say it was a long time ago. It's early days yet.