Because it was levied against immigrants from developed western civilizations presumably because by being successful, they seemed threatening and untouchable with their superior spirits, culture,  and can-do attitudes to the nativist figuratively or literally inbred KKK sort who sought some evil way to take control, divide proud people and traditions of progress, and instead to tilt the civil playing field until it was a preposterously unfair enslaving mess of an artless framework of degradement, one that unduly targeted people for the 'crime' of participating in millennia of honored human culture and tradition.

It was all sold falsely in faux-moralistic terms, kind of like Nixon's sociopolitical war on minorities, liberals, and folks sympathetic to the expansion of minds and spirits. What, did these worthless dangerous wicked arrogantly good-contempting fascists think we were born yesterday or something?