It may be a narrow slice of history but it is a true slice. The wars that have caused death of millions arise from:
a. Religions fighting religions or everybody else.
b. Socialists fighting everybody else or occasionally each other.
Secularism has NOTHING to do with it. Prager is simply wrong.
Prager's arguing that religious America hasn't been more violent or dangerous than Europe was in its most secular of centuries.
Cohen made the assertion that American-style religion was more dangerous than European-style secularism, and so far as I can tell, Prager proved him wrong -- Stalin and Hitler arose in Europe, not in America.
If he goes further and says that secularism as such and in itself has been more dangerous than religion, that's debateable, but he also shows Cohen's trick of defining communism and fascism and nazism as "religions" for the sham that it is.
But Prager may go wrong elsewhere: today's Western Europe is an exhausted society.
Arguably a vital, active society may be more dangerous than one that's become tired out and lost the will to assert its values.
Of course, the problem with that is that weak societies may be dangerous precisely in their weakness and inability to defend themselves.