One of Islam's most revered modern scholars, Sheikh Yusuf al-Qaradawi, openly sanctions offensive Jihad: "In the Jihad which you are seeking, you look for the enemy and invade him. This type of Jihad takes place only when the Islamic state is invading other [countries] in order to spread the word of Islam and to remove obstacles standing in its way." Elsewhere, he notes: "Islam has the right to take the initiative … this is God’s religion and it is for the whole world. It has the right to destroy all obstacles in the form of institutions and traditions … it attacks institutions and traditions to release human beings from their poisonous influences, which distort human nature and curtail human freedom. Those who say that Islamic Jihad was merely for the defense of the 'homeland of Islam' diminish the greatness of the Islamic way of life."
The widely-respected Dictionary of Islam defines Jihad as "A religious war with those who are unbelievers in the mission of Muhammad. It is an incumbent religious duty, established in the Qur'an and in the Traditions as a divine institution, and enjoined specially for the purpose of advancing Islam and of repelling evil from Muslims…[Quoting from the Hanafi school, Hedaya, 2:140, 141.], "The destruction of the sword is incurred by infidels, although they be not the first aggressors, as appears from various passages in the traditions which are generally received to this effect."
Dr. Salah al-Sawy, the chief member of the Assembly of Muslim Jurists in America, stated in 2009 that "the Islamic community does not possess the strength to engage in offensive jihad at this time," tacitly affirming the legitimacy of violence for the cause of Islamic rule - bound only by the capacity for success. (source)
Muhammad's failure to leave a clear line of succession resulted in perpetual internal war following his death. Those who knew him best first fought afterwards to keep remote tribes from leaving Islam and reverting to their preferred religion (the Ridda or 'Apostasy wars'). Then the violence turned within. Early Meccan converts battled later ones as hostility developed between those immigrants who had traveled with Muhammad to Mecca and the Ansar at Medina who had helped them settle in. Finally there was a violent struggle within Muhammad's own family between his favorite wife and favorite daughter - a jagged schism that has left Shias and Sunnis at each others' throats to this day.
The strangest and most untrue thing that can be said about Islam is that it is a Religion of Peace. If every standard by which the West is judged and condemned (slavery, imperialism, intolerance, misogyny, sexual repression, war fare ...) were applied equally to Islam, the verdict would be devastating. Islam never gives up what it conquers, be it religion, culture, language or life. Neither does it make apologies or any real effort at moral progress. It is the least open to dialogue and the most self-absorbed. It is convinced of its own perfection, yet brutally shuns self-examination and represses criticism.
This is what makes the Quran's verses of violence so dangerous. They are given the weight of divine command. While Muslim terrorists take them as literally as anything else in their holy book, and understand that Islam is incomplete without Jihad, moderates offer little to contradict them - outside of personal opinion. Indeed, what do they have? Speaking of peace and love may win over the ignorant, but when every twelfth verse of Islam's holiest book either speaks to Allah's hatred for non-Muslims or calls for their death, forced conversion, or subjugation, it's little wonder that sympathy for terrorism runs as deeply as it does in the broader community - even if most Muslims personally prefer not to interpret their religion in this way.
Although scholars like Ibn Khaldun, one of Islam's most respected philosophers, understood that "the holy war is a religious duty, because of the universalism of the Muslim mission and (the obligation to) convert everybody to Islam either by persuasion or by force", many other Muslims are either unaware or willfully ignorant of the Quran's near absence of verses that preach universal non-violence. Their understanding of Islam comes from what they are taught by others. In the West, it is typical for believers to think that their religion must be like Christianity - preaching the New Testament virtues of peace, love, and tolerance - because Muslims are taught that Islam is supposed to be superior in every way. They are somewhat surprised and embarrassed to find that this is contradicted by the Quran and the bloody history of Islam's genesis.
Others simply accept the violence. In 1991, a Palestinian couple in America was convicted of stabbing their daughter to death for being too Westernized. A family friend came to their defence, excoriating the jury for not understanding the "culture", claiming that the father was merely following "the religion" and saying that the couple had to "discipline their daughter or lose respect." (source). In 2011, unrepentant Palestinian terrorists, responsible for the brutal murders of civilians, women and children explicitly in the name of Allah were treated to a luxurious "holy pilgrimage" to Mecca by the Saudi king - without a single Muslim voice raised in protest.
For their part, Western liberals would do well not to sacrifice critical thinking to the god of political correctness, or look for reasons to bring other religion down to the level of Islam merely to avoid the existential truth that this it is both different and dangerous.
There are just too many Muslims who take the Quran literally ... and too many others who couldn't care less about the violence done in the name of Islam.