If we insist on ignoring our diversity as Shias and Sunnis like those whites who pretend to be color-blind, it would actually contribute to the violence against Shia minorities today. One will become part of this takfiri campagn to discredit Shia Muslims and their services to Islam today. One may be supporting the oppression and discrimination against them and also depriving oneself of the valuable knowledge received from Imam Ali and his family.
The section vs. Shia is a misrepresentation of historical, cultural and academic aspects of both the Islamic schools of thought. Instead of stating everything that has been wrongly stated above, I would just write what is more reasonable and acceptable to readers of both sects of Islam.
Literally, Shia means 'followers' implying 'followers of Ali' and Sunni means those who follow the tradition or tradition of Prophet as reported to them by the companions. Beliefs and practices of Sunnis and Shias differ in many ways although they perform many of the same religious obligations. The main dividing point is the issue of succession of the Prophet (peace be upon him).
Shias believe, based on their understanding of the Qur'an and the historical records, that Prophet Mohammad appointed a successor in his lifetime and did not leave the issue of succession in the hands of the people. This person, according to the Shia beliefs, was Ali the cousin and son-in-law of Mohammad who was the first one to announce his faith at the age of 10, and commanded almost all the battles of early Islam during the Prohet's life.
Sunnis believe that the Prophet did not appoint anyone as a successor and left the matter to be decided by the people after him. Thus they believe that the people had the choice in this matter and they point to the selection of Abu Bakr by a party of people, and silently accepted by the rest, as legimate.
Both have their arguments to support their own view.
The battle in the year 680 C.E. was between Yazid the Umayyid ruler and Hussain the grandson of Mohammad. Yazid demanded allegience from Hussain and threatened to kill him if he did not but Hussain refused to legitimize his authority which he believed was unlawful and tyrannical. Yazid plotted to kill Hussain during the pilgrimage or Hajj, and Hussain decided to leave Mecca a day before the pilgrimage began.
Hussain and other descendants of Prophet Mohammad were killed in a brutal and tragic event where the 30,000 strong army of Yazid denied water to Hussain's camp of 72 men, and their families that included women and children.
Shias emphasize on revelation and human intellect as two pillars of guidance and understanding. Taqiyyah or 'self-protection' means saving one's life when confronted with danger on the condition that it does not lead to destruction of Islam or Muslims.
It is an example of the natural human instinct of self-protection when life is at stake. Taqiyyah is not allowed when it leads to adandonment of rights of people or promotes injustice in any way.
Mut'a sometimes translated as 'temprory marriage' is provision within Quran according to Shia laws which allows a man and a woman to have time-bound relationship requiring a dower for the woman just like regular marriage and requiring the woman to wait for three months at the end of the period. If a child is born he or she is the responsibility of the father and will inherit from him. Woman in this kind of marriage is not a financial responsibility of the man unless documented earlier and during the relationship she does not have to seek the consent of the husband in order to go outside the house.
The section about Assassins being Shias is totally baseless.