Does this mean that Christianity or Judaism are incompatible with democracy? Yes, to the same extent and for the same reasons that Islam is also incompatible. All three are intrinsically ill-suited to be the of a democratic government. They're incompatible because theocracy is incompatible with democracy. Every step that any government takes in providing either recognition or authority to any religion, is a step away from democracy. That's unavoidable, no matter the religion involved. The moment you have a government that acknowledges any religion as the true religion, you have a government in which some animals are far more equal than others.
The Little People, Silly People argument would have it that Islam is particularly poorly-shaped for democracy. However, anyone who doubts that the principles of Christianity can drive just as much violence and intolerance as Islam is ignorant of both history and world events. The history of Christianity is replete with holy empires, holy kingdoms, and holy wars of conquest -- and many of them not comfortably ensconced in the distant past. Everyone who moans that the Ten Commandments should be posted in every school and courthouse, could benefit from contemplating the ultimate fruition of that philosophy in the God's Army militia in Burma. Under the banner of bringing a "government based on the Ten Commandments" to their country, God's Army has killed more than a million people -- far more than al-Qaeda.