It isn't really disingenuous. It's become fashionable to claim that "all graphs should start at zero", but that's not necessarily how you display data. Here is Edward Tufte:
"In general, in a time-series, use a baseline that shows the data not the zero point. If the zero point reasonably occurs in plotting the data, fine. But don't spend a lot of empty vertical space trying to reach down to the zero point at the cost of hiding what is going on in the data line itself. (The book, How to Lie With Statistics, is wrong on this point.)"
He's talking about time-series in this case, but the point remains: you need to understand the data. Sometimes (as in this case, where the trend is important, not the magnitude of change) showing the "zero" point is irrelevant.