This week many Muslims around the world celebrated the holiday of Ashoura. I have found a page, Ashoura in Lebanon, that explains what this barbaric ritual is all about:
The observance of Ashoura is one of the most important events in the Shia calender. Ashoura marks the anniversary of the martyrdom of Husayn, grandson of the Prophet Mohammad, in what is now Kerbala, Iraq. The death of Husayn was the beginning of the Sunni/Shia split, which persists in Islam to this day.
In the past, many Shia men have demonstrated their devotion to Husayn by letting their blood flow freely from self-inflicted wounds. Today, however, many governments have tried to ban this practice, with varying degrees of success. In Lebanon, the practice is permitted, and a bloody commemoration of Ashoura takes place in Nabatieh every year.
Most participants make a small cut on their head, and then beat the wound with their palm--or in this case a sword--to keep the wound open and bleeding. Participants then march in groups around the town, yelling chants to express their devotion to Husayn and the Prophet.
The article above fails to mention that participants also call for the death of Jews, America and Israel. In my opinion, there's a direct link between this culture of blood and death, and the hate and terrorism executed by certain Muslims around the world.