Islam emerged from what is modern day Saudi Arabia in the 7th century, and never looked back. Muslim armies swept across North Africa and invaded Catholic Spain, destroying or converting the Christian communities along the way. They turned churches into mosques, and made Islam the official religion. Muslim armies also took over the Holy Land, destroyed the last non-Islamic Persian empire, and moved into Asia Minor (modern day Turkey). By the 16th century, Islam had destroyed the Christian Byzantine Empire, had taken over Constantinople, and had turned the Hagia Sophia -- the most beautiful church in Christendom -- into a mosque. A century later, Muslim armies were outside the gates of Vienna.
While the years have passed and the names of the armies and countries have changed, Islam's war against the rest of us continues at full speed. There isn't a day that goes by without a new terrorist attack carried out by a Muslim militant. Women are stoned in Afghanistan because they had the nerve to be raped... Children are beaten to death and strung up in Pakistan, because they were suspected of theft... Non-Muslims living in Muslim countries are in constant fear of kidnapping and murder... It's even happening here. In Buffalo, New York, a Muslim-American television executive who attempted to use his station to improve U.S public opinion about Muslims later beheaded his wife after she filed for divorce. Of the roughly 25 wars currently ongoing, 21 involve Muslim countries. Put differently, Islam is connected to 80% of the planet's armed conflicts, while making up only 20% of its population. There's a reason for that.
In Islam the world exists in two Houses. The House of Peace, where Islam is the recognized religion, and the House of War, where Islam is fighting to become the recognized religion, and because Islam teaches that Allah may change his mind at any time, for Muslims, there is no stable and universal moral code. When you eliminate reason as a guide in human thinking, force is the only thing that determines truth. For that reason, in the House of War, anything goes.
In regard to the Park51 mosque, both critics and supporters are getting the context wrong. They're framing the debate as if it were a New York or American affair -- a local dispute over land use. This is dangerously naive. The context isn't New York in the year 2010, but the whole world since the seventh century. If you ignore that, you miss the entire point, and are reduced to explaining the protests as examples of bigotry or religious intolerance.
Islam has always grown through conquest, never through peaceful conversion or persuasion. Furthermore, there is nothing in Islam that allows for religious freedom, because Islam rejects the use of reason. If you can't depend on reason, then what's the point of having the freedom to use it? After all, it will only mislead you. In Islam, you're expected to submit to God (as he is presented to you by Islam), no matter what your reason or logic tells you.
That theological point has real-world consequences: The God of Islam will do what he will do, when he wants to do it, and there's no telling what that might be. God might make the sun rise tomorrow... Or he may not. He may upend the laws of gravity, or he might maintain them. We don't know, it's all up to Allah. That means we don't live in a stable natural world, and science is therefore impossible. That's the reason the Islamic world has fallen so far behind in technology, science, and medicine -- because they've rejected its very foundation. That's also why democracy is ultimately incompatible with the religion: If you can't depend on reason, how could you successfully choose a leader? Instead, a leader will be chosen for you by whatever Islamic authority has jurisdiction.
Contrast that with the attitudes of both Christianity and Judaism throughout history. While both have had (sometimes serious) conflicts -- and have carried out periods of religious suppression -- they both share a devotion to God-given human reason. Think of what that makes possible: People can be persuaded through argument, and not violence. Might no longer makes right. When Christians and Jews have violated this in the past, it is because they have acted contrary to the foundations of their religions, not because of it.
This devotion to reason also creates room for religious freedom. If we can use reason as a guide, then truth -- if presented fairly -- will be more compelling than error. We don't need to impose our religion through force (as is the case with Islam), but can simply create a free society where people can make their own decisions about faith and government. They'll sometimes be wrong, but when they are, it's because they neglected some aspect of their reason.
Islam is entirely different. They rejected philosophy in the 11th century, and have been in a cultural free fall ever since. Muslims are fine with religious freedom when they're in the minority in a country, because it gives them room to grow. But once they become the majority, they transform the nation into something else entirely, because a liberal democracy run by human reason is an offense (and an impossibility) to the Muslim Mind. Islam doesn't thrive in a liberal democracy; it merely bides its time.