Graetz & Shapiro want to understand how the political culture shifted from one in which people thought that wealthy people ought to support the society that made their wealth possible, to one in which people hope to get rich enough to worry about inheritance taxes, and thus take a preemptive dislike to them.
I think that one difference may be that society does less to "make it possible" for people to get wealthy now. A hundred years ago, or even fifty, the politics of inheritance taxes were different. But then the government mostly defended the country and engaged in various public-good activities, like building roads or supporting research. There was pork, and income transfer, of course, but it was a much smaller part of the picture. So the notion that one was "giving back" to a system that made wealth possible made some sense.
Now much of the government's taxing-and-spending is about transferring money from one group to another. The "give back" point is much weaker, because the system isn't about public goods, but about payouts that are (usually) driven by interest-group politics rather than the common good. So the moral claim for inheritance taxes would seem to be a lot weaker, and maybe it's no surprise that many people see it that way.
On the other hand, as the book also looks at political tactics, let me suggest that "fuck the small businessman" is a poor slogan for those favoring inheritance taxes.
I think he's right.