Why Islamic terrorists do what they do

This is a particularly interesting article from the former professor of Islamic history at Al-Azhar University,Cairo - the most prestigious Islamic Univeristy in the world. Able to quote the entire Quran by the age of twelve, Dr. Mark Gabriel now resides in the United States after being disowned by his family and threatened with death after converting to Christianity.

As a freshman college student, Gabriel says one of the most popular lecturers was a blind Sheik. Gabriel asked why he never talked about the love, peace and forgiveness in Islam. Angered, the sheik said, "Jihad and killing are the head of Islam. If you take them out, you cut off the head of Islam." That blind man was Omar Abdel Rahman who was convicted of masterminding the 1993 World Trade Center bombing. Before he came to America, he was the spiritual leader of the radical Egyptian group al-Jihad, which killed President Anwar Sadat ...

Muhammad's life and teachings have served to establish principles of warfare and coersion that are practiced today. The revelations he received are dictated by periods in his life. When there is a contradiction in Quranic verses (which Gabriel questions), Islamic scholars had to determine which verses to follow. "This was accomplished by the principle of naskh," which means that the new revelations would override previous revelations.

There are at least 114 verses in the Quran that speak of love, peace, and forgiveness ("The Heifer" Surah 2:62, 109). "But when Surah 9:5 was revealed later, it canceled out those previous verses," Gabriel says. "This Surah is known as the 'verse of the sword," and it explains that Muslims must fight anyone who chooses not to convert to Islam, whether they are inside or outside of Arabia. It is considered to be the final development of jihad in Islam."

JIHAD...

Jihad (holy war) is a command to all Muslims enforced by the Quran. The focus is to overcome people who do not accept Islam. Islam is a religion of works. Dying in jihad is a great honor, and it is the only way a Muslim is assured of entering Paradise at all. This is why you see Muslims leaving their own nations to fight jihad in other countries. "Their motivation is religious, which is much more dangerous than a political motivation," Gabriel says. Jihad is the motivation behind almost every act of terrorism done in the name of Islam.

The whole article can be read here

What's presented here is a bit oversimplified. Jihad in islam has a few meanings (as I was told by a few Arabs I met). It also means "struggle" in the spiritual sense. Also, the violent form of jihad is embraced by well, violent followers of Islam, who by the way are a minority in that religion.

In practice, islam often coexisted with other religions on same territory.
Yes, it does have extremely violent pages in its history, just like any other major religion.