During the Vietnam War, Hannah Arendt noted that members of the Democratic Administration had frequent recourse to phrases like "monolithic communism," and "second Munich," and deduced from this an inability "to confront reality on its own terms because they had always some parallels in mind that 'helped' them to understand those terms."
When I was college, it was common for student activists to call slavery "the Black Holocaust" or "The Real Holocaust." There's an argument to be made about America, and the stories we tell ourselves when we see ourselves as heroic, and when we don't. But most of these activists--some of them anti-Semites--knew very little about Jews, Europe, Nazism nor, frankly, slavery. And they didn't much care. They were not interested in specifics. They were interested in leveraging the moral power of other people's experience, in order to bolster the moral power of their own. It was narcissism, laziness, and basic lack of respect--not simply for the Jewish experience--but for the specifics of the African-American experience.
I've stated my distaste for the appropriation of "Holocaust" to other contexts in general. And I think that Coates is right both that such a move is both demonstrative of a lack of imagination, and represents an astoundingly disrespectful attempt to leverage one group's experience on behalf of another (often without that group's consent, and often -- as Jews well know -- against the group itself).