Slaves in the attic: how many is too many?

It looks like the State of Maryland is on its way to apologizing for slavery. The Senate has unanimously done so, and it seems the House is poised to pass its version.

I can't find a second source on what's up at the University of Maryland, but according to Mark Graber, who teaches there,

The University of Maryland is debating whether to apologize for slavery. An only slight exaggeration of the state of the debate is that the University will apologize if the evidence demonstrates more than one-hundred slaves toiled on campus, are undecided about an apology if the number was between ten and a hundred, and will not apologize if the number was less than ten.

Can this be serious? Like Yale, which insists, as if it's terribly relevant, that Elihu Yale didn't actually own slaves and so his portrait with a slave must come down, it seems a bit literalistic. It seems to assume that only the people who owned or employed slaves reaped the benefits. I suppose it's the same kind of thinking that resists modern-day apologies of any kind: we didn't own slaves, so what is there to say?

I'm not entirely sure what I think of apologizing for slavery. It could ring hollow. But I think Graber is right about what it might be able to do:

I do not know whether all of this warrants an apology or reparations. On the one hand, neither resolves an extraordinarily deeply rooted problem. On the other hand, no better immediate solution exists. Perhaps the best we can do is convert demands for apologies for slavery and investigations into the direct presence of slavery into investigations of the pervasive influence of slavery and race on all aspects of American social, political, and life. Slavery and race were not the sort of warts on the American polity that could be easily excised by the 13th Amendment or Civil Rights Act of 1964. They are cancers that are so entwined with normal practices as to resist almost all efforts at social, legal and political eradication. Our students need to be aware of just how pervasive slavery and racism were and are, and this knowledge cannot be gained by limiting the debate to whether or not a specified number of slaves worked in specific places in specific times.

More on the subject of the indirect but pervasive legacy of slavery in Graber's review of Robin L. Einhorn, American Taxation, American Slavery--"a powerful contribution to the now dominant view among scholars that slavery was such a significant, even a foundational institution in the early United States that it affected almost everything that happened in the political arena.'"