Newly inaugurated Iranian president Hassan Rouhani last night refused to answer a direct question from NBC journalist Ann Curry regarding his stance – agree or disagree – on statements made by his predecessor Mahmoud Ahmadinejad questioning the historical reality of the Holocaust. Rouhani answered “I’m not a historian, I’m a politician.”

The refusal to acknowledge that six million Jews were murdered by Nazi Germany has become a kind of proxy for the degree to which various Iranian leaders are understood as relative pragmatists, and much has been made by Western analysts of statements made by Foreign Minister Mohammed Javad Zarif to the effect that Iranian leaders have never in fact denied that the Holocaust occurred.

The claim is difficult to square with, among other things, boasts by Ahmadinejad claiming that his greatest achievement was mainstreaming Holocaust denial...