The problem with that analogy is that most Christian theologians do not adhere to Leviticus literally. By contrast, most muslim theologians - including the "mainstream" ones - profess an extremely literal adherence to the Koran.
This is no fluke coincidence. Even Ibn Khaldun and Al Ghazali, two widely influential "mainstream" muslim thinkers, expressed a belief in jihad and asserted that only Islamic governments were legitimate. The radicals like Ibn Taymiyya, Muqtada al Sadr, and Said Qutb, of course, go far beyond those already extreme premises. In the greater realm of muslim theological consensus, those who do not take the Koran's mandates for jihad and islamic theocracy literally are in fact a small minority.
The "radicals" you cite are from the 14th, 21st and 20th centuries. I would imagine that they go beyond the "extreme premises" of ibn Khaldun (whose work I know better), just as Pat Robertson or William Pierce go beyond the "extreme premises" of Machiavelli.