Iconoclasts (Greek, "image breakers"). Reformers who rose in the eighth century, especially averse to
the employment of pictures, statues, emblems, and all visible representations of sacred objects. The
crusade against these things began in 726 with the Emperor Leo III., and continued for one hundred and
twenty years. (Greek, ikon, an image; klao, I break.)

Now used principally to refer to people who try to overthrow traditional values or beliefs