King alone among contemporary heroes is worthy of a national holy day not because he mixed faith and politics, nor because he enunciated a sentimental dream. It was because he represented something truly terrifying.

When King was shuttling back and forth to Memphis in support of striking garbage workers, Tennessee Governor Buford Ellington typified the conservative establishment’s understanding of him: He was “training 3,000 people to start riots.” What looks today obviously like transcendent justice looked to conservatives then like anarchy. The conservative response to King—to demonize him in the ’60s and to domesticate him today—has always been essentially the same: It has been about coping with the fear that seekers of justice may overturn what we see as the natural order and still be lionized. But if we manage to forget that, sometimes, doing things that terrify people is the only recourse to injustice, there is no point in having a Martin Luther King Day at all.