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Yes, they are just tribal groups (see post #10). And then over it all they have the nasty Sunni/Shia schism for their global-level hatreds.

Not just Shia/Sunni and almost all consider the others to be apostates and worthy of punishment leading to death.

DIVISION of ISLAM
1 Shia Islam
1.1 Twelver
1.2 Ismā'īlīsm
1.3 Zaidiyyah
2 Sufism
2.1 Bektashi
2.2 Chishti
2.3 Naqshbandi
2.4 Nimatullahi
2.5 Oveyssi (Uwaiysi)
2.6 Qadiri
2.7 Suhrawardiyya
2.8 Muridiyya
2.9 Tijaniyya
2.10 Shadiliyya
2.11 Mawlawiyya
3 Ahmadiyya
3.1 Ahmadiyya Community
3.2 Lahore Ahmadiyya Movement
4 Kharijite Islam
4.1 Ibadi
5 Other Sects
5.1 Quranism
5.2 Moorish Science
5.3 Nation of Islam
5.4 Mahdavism
5.5 Messiah Foundation International
5.6 Zikri
5.7 Five Percenter

Worse than this is the wide bunch of Christian sects, but at least they don't behead each other (anymore). First the Catholic Church, then the split into Roman and Eastern, then the split off of the various Protestant sects, way too numerous now to list.

I guess heresy and apostasy is an inherent feature of all religious groups.