There's been a lot on the internet in the past few years, on why Islam is worse than all other religions. Or, conversely, why Islam is not worse than all other religions. And it seems to me that both sides manage to obscure Islam's most important practical difference with most religions in the world today.
As an atheist with a morbid fascination with religion I would like to offer my own observation:
Lots of people talk about America's separation of church and state like it is a radical concept, for better or for worse; and it is true that in Europe the separation is a little squishier. But I would like to postulate that the separation of church and state is fundamental in human society and psychology, and we post Enlightenment westerners have simply been especially clever in codifying it.
Consider: Any stone age tribe that can afford it, and many that cannot, will have both a shaman and a war chief. The priests and the kings are clearly two different power structures with friction between them in Homeric Greece; I point to Agamemnon's line in the Iliad that priests (who precipitated his dust up with Achilles inter alia) have brought him nothing but trouble. The Pontifex Maximus of ancient Rome was forbidden being anywhere near blood - i. e., he was NOT to be leading any troops anywhere, a clear indication that ancient Rome separated priestly from kingly functions. And of course this dichotomy is all over the Old Testament in the time of King David, before, and after.
Nor was there some kind of magical confluence of Church and State in medieval Europe, as some Christians I have conversed with have wistfully claimed. Church and State in Christian Europe were always independent power structures, with interests that sometimes overlapped and sometimes conflicted violently. Christianity's first three centuries as an ANTI-State religion contributed to this, no doubt, as did the juxtaposition of usually-celibate priests vs male primogeniture in kingdoms. But as I said, some level of separation of religion and state function seems to be very basic in human societies, and it really should not be surprising.
There are probably good social-psychological-survival reasons for religion and executive power being at least somewhat separated in so many human societies. I cite the example of the famous Tecumseh and his brother Tenskwatawa the Prophet. Tecumseh was a good military and political leader; whereas Tenskwatawa had rhetoric that could move great masses of Native Americans of various tribes. Together they were a serious threat to the U.S. army. However, when Tenskwatawa assumed leadership while Tecumseh was off doing good war-chief stuff like gathering allies, the Prophet proved his complete ineptitude at military leadership, provoking the battle of Tippecanoe and the burning of Prophetstown. (Similar, literally pre historic events probably had provoked the rule for the Pontifex Maximus in ancient Rome.) Running a religion and talking to Gods is really a very different enterprise than leading people into war, and requires at the least a different mindset. Priest and King may work in concert, towards common goals, as with Deborah and Barak, or Tecumseh and his brother; but for the good of the Tribes they lead they REALLY should not be the same person.
OK, so what about Mohammad? He was unluckily the exception to what seems to be an almost universal rule here. He was (through fortunate selection of his military subordinate) both a successful prophet and a successful war chief. He never in his lifetime accommodated even whatever modest separation of powers might have held sway at that time in ancient Arabia. He was not only both a very successful prophet and war chief, he was judge, jury and executioner. And this abnormal situation is all very clear in the Koran, crystallized in the words of the Prophet as the proper state of Man.
Obviously that severe interminglement waned in many later Islamic societies. The Ottomans, for example, developed (and adapted from the Byzantines) bureaucracies where there was more of a traditional division of labor; though the Caliph might have theoretical ultimate religious power, in practice he deferred to the clergy for this, and concentrated on collecting taxes and making war and other traditional kingly duties. It's a natural, human tendency to divide tasks among people based on their actual abilities, and Moslems have that tendency too.
There are clearly Muslim secularists out there, who want to see Islam in a more conventionally religious role alongside a state which wields a more conventionally secular power. And probably they will eventually prevail and reform Islam in the process.
In the meantime though, there is a real problem with saying Islam is just a religion like any other. That is, that any Muslim reformer who tries to separate Church and State (other things too, but that's a biggie) can be attacked by a more orthodox Muslim who can, legitimately, claim that the reformer is departing from the ways laid down by the Prophet himself. This has happened repeatedly in the internal politics of Muslim countries.
It's not going to be an easy bar for Muslim reformers to get over, is all I'm saying. Nonetheless it will have to happen eventually. The alternative is essentially Muslim mass suicide. It is just NOT a good survival tactic to permit people who think they talk directly to God to lead you into politicoreligious wars against nations with superior firepower. As a bunch of Shawnees in Prophetstown learned the hard way.