> [People in dictatorships] may be less vulnerable [than people in democracies] to attacks from outsiders, but they are much more vulnerable to attacks from their own government.

What the study is saying is:

> Our research implies that insider attacks from within American politics can be more pernicious than attacks from other countries.

That is, I'm comparing the vulnerability of people in democracies to people in dictatorships; the report is comparing the vulnerability of people in democracies to attack A or attack B. We're not disagreeing.