The April 7 edition of Time includes an article by Richard Lacayo hailed the peace symbol, "50 years old and still working." It was the ready-made icon for the sixties counterculture. But then Lacayo decided to compare it to the Christian cross, and things got ugly:

There were people who didn't like the symbol any better than they liked the movements it represented. They saw it as an inverted broken cross or "the footprint of the American chicken." But it kept spreading through the culture. Like the Christian cross, which has served the purposes of soup kitchens and Crusaders, the Sisters of Mercy and the Ku Klux Klan, it was adaptable. Over time, it evolved from its narrow association with nuclear disarmament into an insignia for countercultures of all kinds. Hippies made it a sort of all-purpose symbol of peacefulness. The environmental group Greenpeace, the militant wing of flower power, adopted it for its eco-defense campaigns.

While the Klan and the burning cross certainly go together -- and the Klan definitely saw itself as righteous Christians -- this is still a bit of free association that burns and singes the vast majority of Christians (including black ones) who loathe the Klan.