Our Sunni brothers and sisters are quick to dismiss the question of succession to the Prophet as an historic issue with little modern relevance. However, such quick dismissals lack proper understanding regarding the chaos and instability that followed the demise of the Holy Prophet.
It was only logical for the Prophet to appoint a vanguard who would lead the believers socially and politically after the Prophet. When this leader was abandoned, things spiraled downwards. By forsaking their Divinely-chosen leader, the Muslims had essentially created an authority vacuum in the Muslim world. In the time of the Prophet, he was considered the final arbitrator and authority on all personal, religious, social, and political matters. Religious legitimacy for any action was derived from the Prophet's approval, not from political or personal motives. Within the next two centuries, the leadership of the Muslim world became an entirely political office, albeit one that claimed religious legitimacy for its various military and genocidal extravaganzas as far east as India and as far west as Spain. Every single atrocity committed by Muslims – whether it was aimed at the Prophet's own household, the Hindus of western India or the Bedouins of North Africa – was deemed permissible through some sort of religious interpretation.
The practice of twisting Islamic teachings into supporting personal and political agendas was seen best on September 11, 2001, when a group of men claiming to be followers of Islam flew airplanes into the World Trade Center, the Pentagon, and almost the White House.
While both Shias and Sunnis were quite vocal in condemning the acts of 9/11 as un-Islamic, the question remain for our Sunni brothers and sisters: if you say that Osama bin Laden's interpretation of Islam is incorrect, then who exactly has the right to interpret the teachings of Islam? If you do not believe in a Divinely-appointed religious authority, what makes your interpretation of Islam any more valid than that of bin Laden? By abandoning the Prophet's appointed successors, you have opened a Pandora's box of contradictory and inhumane interpretations of Islam, with no definitive authority on deciding what exactly is "true Islam".
By asking for a pen and paper on his deathbed, the Holy Prophet had wanted to ensure that the Muslim world would not have to face such situations. By centralizing the source of religious authority within the Pure Ahlul Bayt – individuals whose spiritual purification, infallibility, and authority over the believers have been confirmed in the Qur'an and Hadith on numerous occasions – he wanted to eliminate the possibility of Islam being exploited for personal and political gains. As such, while the Muslim world throughout history found imposed upon itself cruel and oppressive tyrants, whose cruelty and tyranny was justified by religious "scholars", the followers of Ahlul Bayt gave their allegiance only to the Divinely-ordained representatives of God on Earth. While the Muslim world today finds itself constantly apologizing for the atrocities committed by its present and past notables, the followers of the Ahlul Bayt can truly hold our heads up high for having followed leaders that received their inspiration from God Almighty Himself. As the Dalai Lama himself said, "If we had Ali's Nahjul Balagha and Hussain's Karbala, the whole world today would be Buddhist!"
As we commemorate the demise of our Holy Prophet, let us recall the phrase that we are recommended to utter on the Day of Ghadir: "Praise be to Allah, for He included us among the followers of Amirul Momineen and his Infallible Offspring." Let us mourn the death of God's greatest servant, but let us also thank Him for including us among those who never lack guidance, those who still have a Rightly-Guided Guide, those who never have to apologize for the past, and those who have found salvation through the most important principle laid down by the Prophet for mankind till the Day of Judgment: "I am leaving behind two precious things: the Book of Allah and my Progeny, for indeed, the two will never separate until they come back to me by the Pond of Kawthar."