[delib]

> be much better supported by typical social science approaches

This implies that linear regression is not a typical social science method. If you review articles in sociology or political science journals, you will find that many articles use quantitative methods, and nearly all of those quantitative articles use regression.

They also attempt to get at the causality implied in their hypothesis. It's hard to do that purely with qualitative methods. Not everybody might find their IV regression convincing (they rarely are), but it's good to see that they tested their hypothesis with data.