That is their way of justifying the murder of American diplomat John Granville in 2008.
Via Raymond Ibrahim:
Arguing that Muslim blood is more precious than infidel blood, Muslim clerics in and out of Sudan are outraged because a Sudanese court has condemned a Muslim man to death—simply because he murdered a non-Muslim, the American diplomat John Granville on January 1, 2008. […]
Finding the punishment unjust, several international Islamic organizations, most recently, the London-based Islamic Media Observatory, have been trying to commute the death sentence, mostly by arguing for Abdul Ra’uf’s “human rights.”
However, the Legitimate League of Scholars and Preachers in Sudan (an influential body of Muslim clerics) issued a statement last month titled “Let no Muslim be killed because of an infidel”—a verbatim quote, in fact, from Islam’s prophet Muhammad—revealing the true reason why so many Muslims are trying to overturn the death sentence.
The Arabic language statement begins by asserting that “Allah has honored human beings over creation and multiplied the Muslim’s honor over the infidel’s, because Islam elevates and nothing is elevated above it. The value of the blood of Muslims is equal, or should be, but not so the value of the blood of others.” (The Koran itself, e.g., 2:221, confirms this idea that even the lowliest Muslim is superior to any non-Muslim.)
Next, the statement quotes the clear words of Islam’s prophet, Muhammad, as recorded in a canonical hadith: “Let no Muslim be killed because of an infidel.” It then elaborates on the meaning of this statement by quoting from “the consensus of Islamic scholars,” or ijma‘, a legitimate source of Islamic jurisprudence.