Yeah the roman salute used to be used by the romans and others.
Then it was used by the nazis. So just like the name Hitler and the toothbrush mustache, it's not indelibly tainted by the Nazis and has come to represent nazism in the western world. Especially in... oh, you know, Germany.
Blame the Nazis if you want, but them's the brakes. No need to be dense about it.