Wikipedia*, the toothbrush-style mustache became popular "as a response by working-class men to the flamboyant, flowing Kaiser-style mustaches of the upper classes". Or at least, I would imagine, those wishing to express such sympathies. Would the Hillary bowl, Kerry hunt, or Bush brush-cut would be similar such examples of cynical shibolethery.
At any rate, not only was Hitler responsible for horrendous crimes against humanity, but he single-handedly destroyed the toothbrush mustache. Has there ever been such a fashion disaster?
*a BBC article is referenced, which in turn quotes a comedian as an authority. Oh, Wikipedia.