Iran was most vocal against Salman Rushdie because he is a Shia Muslim by birth. Many Sunni Muslim do not consider Shia as Muslim and did not pronounce any death penalty for The Satanic Verses written by a Shia Muslim. But Iran wanted to promote herself as true leader of Islam and a blasphemous novel in eye of Islamic world from a Shia Muslim (by birth) can not be tolerated by Iran's Shia leaders.
British Airways flight diverted to Canada after bomb threat (AP)
from the article: Salman Rushdie, and the right to offend