Sectarianism, according to one definition, is bigotry, discrimination or hatred arising from attaching importance to perceived differences between subdivisions within a group, such as between different denominations of a religion, class, regional or factions of a political movement.

The ideological underpinnings of attitudes and behaviours labelled as sectarian are extraordinarily varied. Members of a religious or political group may believe that their own salvation, or the success of their particular objectives, requires aggressively seeking converts from other groups; adherents of a given faction may believe that for the achievement of their own political or religious project their internal opponents must be purged.

Sometimes a group that is under economic or political pressure will kill or attack members of another group which it regards as responsible for its own decline. It may also more rigidly define the definition of "orthodox" belief within its particular group or organisation, and expel or excommunicate those who do not support this newfound clarified definition of political or religious 'orthodoxy.' In other cases, dissenters from this orthodoxy will secede from the orthodox organisation and proclaim themselves as practitioners of a reformed belief system, or holders of a perceived former orthodoxy. At other times, sectarianism may be the expression of a group's nationalistic or cultural ambitions, or exploited by demagogues.

Mehdi Hassan Khan (Urdu: مہدی حسن خان ) is a Pakistani ghazal singer and a former playback singer for Lollywood. He is famously known as the 'King of ghazal' (Urdu: شہنشاہِ غزل). He has ruled the Pakistan film industry along with Ahmed Rushdi. He was honoured with Tamgha-e-Imtiaz, Pride of Performance and Hilal-e-Imtiaz by the Government of Pakistan, and Gorkha Dakshina Bahu by the Government of Nepal.

Mehdi Hassan was born on 18 July 1934 in a village called Luna in Rajasthan, India into a family of traditional musicians. He claims to be the 16th generation of hereditary musicians hailing from the Kalawant clan of musicians. Mehdi Hassan had his musical grooming from his father Ustad Azeem Khan and uncle Ustad Ismail Khan who were both traditional Dhrupad singers. Hassan started to perform at a young age and the first concert of dhrupad and kheyal with his elder brother is reported to have been held in Fazilka Bungla, near present DC House (1935) of Undivided Punjab. After the Partition of India, 20-year-old Hassan and his family migrated to Pakistan and suffered severe financial hardships.

Hamza Yusuf Hanson is an American Islamic scholar, and (with Zaid Shakir and Hatem Bazian) is co-founder of Zaytuna College in Berkeley, California, United States. He is a convert to Islam, and is one of the signatories of A Common Word Between Us and You, an open letter by Islamic scholars to Christian leaders, calling for peace and understanding. He has described the 9/11 attacks as "an act of 'mass murder, pure and simple'". Condemning the attacks, he has also stated "Islam was hijacked ... on that plane as an innocent victim".The Guardian newspaper in the United Kingdom reported that he "is arguably the west's most influential Islamic scholar" and added that "many Muslims find his views hard to stomach."

Hamza Yusuf was born to two academics in Washington State and raised in Northern California. In 1977, he became Muslim and subsequently traveled to the Muslim world and studied for ten years in the United Arab Emirates, Saudi Arabia, as well as North and West Africa. Hamza Yusuf spent four years studying in the United Arab Emirates and elsewhere in the Middle East. Later he traveled to West Africa and studied in Mauritania, Medina, Algeria, and Morocco under such scholars as Murabit al Haaj; Baya bin Salik, head of the Islamic court in Al-'Ain, United Arab Emirates; Muhammad Shaybani, Mufti of Abu Dhabi; Hamad al-Wali; and Muhammad al-Fatrati of Al Azhar University in Cairo, Egypt.^{[citation needed]} After more than a decade abroad, he returned to the United States and earned degrees in nursing from Imperial Valley College and religious studies at San José State University.^{[citation needed]}