Boxill does two interesting things.
First, he draws a distinction between forwards-looking and backwards-looking moral considerations. He calls the former “compensation” and the latter “reparations.”
Second, he constructs a very simple case involving a stolen bicycle to blunt the two most common objections to reparations for historic wrongs.
In the second variation of the case, an innocent person, Harry, receives the stolen bicycle; despite his innocence, Boxill argues, he has to return it to its legitimate owner.
In the third variation, the original owner, Tom, dies. So it is impossible to return the bicycle to him. Nonetheless, Boxill argues, the bicycle still has to be returned. In this case, it has to go to Tom’s heir, Jim.
This is relevant because the most obvious thing to say in response to being asked to pay reparations for historical injustice is “I didn’t do anything wrong!” The second most obvious thing to say is, “the victims of the injustice are long gone.” Both points have the virtue of being true. So it’s important to know if there is reason to doubt that they carry as much moral weight as they seem to.
I think it’s helpful to separate at least three questions about Frum’s points.
First, is what he says true? You might deny that the facts he presents are accurate or that they have the significance he attributes to them.
Second, are they logically relevant? Points that are relevant for forward looking reasons are not obviously relevant to a backwards looking case. (I’m not saying they aren’t relevant at all. It’s very hard not to give forward looking considerations a lot of weight. I’m just saying that you have to pay attention to what argument you’re disputing.)
Third, do they point out inherent flaws in reparations schemes? In other words, could there be a way of designing reparations payments to avoid the problem?
There are doubtless other questions you should ask in addition to these. Just be clear about exactly how a given argument is supposed to support or undermine the proposal at hand.