Historically, little more than a rhetorical device, takfir has in recent years grown into a deadly weapon in the hands of Muslim extremists bent on purging Islam of just about anyone who does not subscribe to their views.
Wait a minute! I thought all Muslims thought alike. At least that's what the Nuke Mecca says. Could it be that they're wrong?
All muslims agree on killing all non-muslims. Or at least saying they don't want to kill all non-muslims while actively pursuing the death of all non-muslims.
They need to ramp up the muslim/muslim murders regardless.