This is a very broad topic with a long history so I will try to mention a few points here:
• Religions nowadays have many sects such as with Christianity (Greek Orthodox, Catholic, Protestant, Jehovah’s Witness and more) and Judaism (such as Orthodox). Likewise, there are sects in Islam such as Shia, Sunni, Burailwi, Sufi, Qadiyani and many more
•The Prophet PBUH prophesied that religions would eventually have sects -Christianity and Judaism as well as Islam. However, this does not mean that people should create sects and divide themselves
• Historically, conflicts have occurred between sects such as between Catholic and Protestant Christians. An example of this was the Gunpowder Plot on 5 November 1605 in England where Guy Fawkes tried to destroy the House of Parliament (centre of government) but was caught. You can read more about this from here:
• Regarding Shia and Sunni Muslims; this is a very long topic and I am not specialised in it. The gist of the difference is that there are Shia who believe that the leaders of Muslims should be direct descendants of the Prophet PBUH so they believe that his cousin, Ali, may Allah be pleased with him, should have been his successor and not his other companions such as Abu Bakr, Omar and Othman, who are seen by Sunni Muslims as some of the greatest companions and three of the four “Rightly Guided Caliphs”, may Allah be pleased with them. Many Shia do not like them as they believe they unlawfully succeeded the Prophet PBUH. I Have tried to give an overview of this part of history by speaking about Ali, the cousin of the Prophet PBUH and his family through my series “House of Fatima”. You can watch it from here:
• There is a difference between politics and what common people think. For example, one might believe that there is great hatred between everyone from India and Pakistan. However, in a neutral country such as the UK where you have many British Indians and Pakistanis, you might not feel any hatred between them because of their origin
• Not everyone is religious and /or takes an interest in history so they are born into a religion without fully understanding it or agreeing with its doctrines. To them, it might not make any difference what religion or sect someone else belongs to or the differences associated with them
All of these issues might make the reader wonder; which sect is correct? Without directly advocating for or against any sect, I would recommend that generally with anything (not only this article but in other areas of life), people should question what they read or hear and not simply believe everything based purely on rumours or what many people think. I would also advise that people should do their own background reading to check how accurate the information is and whether it is valid or not, going back to the original sources of information as much as possible, thus allowing them to decide for themselves. In this case, I would advise the reader to go back to the Quran and Hadith (sayings of the Prophet PBUH) and see what they actually say about the various beliefs such as the companions and the Prophet PBUH. Beyond that, I would recommend reading historic accounts and perhaps asking someone specialised in the field.
One reason that I personally would not follow other sects is because of what was mentioned in the Quran: “This day have I perfected your religion for you and completed My favour unto you, and have chosen for you as religion AL-ISLAM” (Surah Al Maida 5:3). To me, this suggests that the religion is complete -but is this something that you agree with? What do you think?