Surely it would be appropriate for Western governments to express sympathy and horror to Tehran and Iranians over yet another ISIS terrorist attack on civilian institutions in an urban center--just as they would do if such an attack happened anywhere else.

It would be the decent and consistent (i.e., non-hypocritical) thing to do, and it would generate a lot of goodwill between Iran and the West, which is surely a good thing.

Alternatively, the West can present a unified front behind President Trump in celebrating any Sunni action to isolate and undermine Iran.