I think there's a much simpler reason that swastikas remain taboo: they still mean hate and belief in the superiority of one race (defined by convenience, as always) over another to those perpetuating the hate. There are Americans, South Africans, and other European descendants who, finding themselves woefully unable to cope with the intellectual and self-disciplinary demands of reality, still latch onto the idea that their problems are not caused by themselves but by others, and they wave this flag to represent their membership in the tribe that was so powerful it took the rest of the world to stop it. In Germany, those whose hate was suppressed by the government went underground, and their grandchildren now protest in the streets of reunified Germany and wave the flag their grandparents made infamous. They make fools of themselves by claiming the death camps forgeries but continuing to hate the same people we all know were slaughtered there.
Keeping the swastika a taboo may help the rest of us by letting these people identify themselves through their use of this and other symbols, but it may also perpetuate their power. If the swastika were a "lucky charm" inside every box of breakfast cereal, would it still hold the power it does? Would new initiates of hate still feel a rush of adrenaline seeing this taboo symbol brazenly displayed?
There is other hate in the world: witness, Bosnia; witness, Rwanda. The Cerbs and the Hutu did not wave flags bearing this symbol, but they are alive today and still killing. Maybe the trigger for our anger should not be the name "Nazi" or the symbol of the swastika, but the evil acts carried out under them, because we seem to be blind to hate not carrying the flag of Nazi Germany.