Well, I can sort of understand the thinking although I would think a Star of David would be a better symbol to use as representative of Judaism. A menorah is often associated specifically with Hanukkah... ergo, not as "secular."
But then there are associations that come to mind with any symbol over and above just that of naming a religion. The cross symbolizes Christianity, yet it is also associated specifically with Easter... ergo also not "secular."
Generally, I like the Star of David as representative of Judaism because it really isn't associated with any particular holiday etc. and it's sort of generally generic... ergo "secular."