“As for those who divide their religion and break up into shias (sects), you have no part in them in the least: their affair is with Allah: He will in the end tell them the truth of all that they did.” (Quran, 6:159)
“…and be not amongst those who join gods with Allah, those who split up their Religion, and become shias (sects) – each party rejoicing in that which is with itself.” (Quran, 30:31-32)
“Truly Pharaoh elated himself in the land and broke up its people into shias (sects) … for he was indeed a maker of mischief.” (Quran, 28:4)
We learn from the Quran (the verses cited above) that dividing religion into sects is akin to joining partners with Allah, an unforgivable sin. The reason that creating a religious sect is considered associating partners with Allah is because it is playing the role of Allah since Allah alone has the right to create a Deen (faith). These people who create sects are trying to take over this role of Allah and put themselves on par with Him.
It does not matter what a person calls his or her sect–it is not authorized by Allah. Allah condemns all sects, and those who break away from the main group.
Allah Almighty says in the Quran: “This Day I have perfected your Deen for you and chosen Al-Islam to be your Deen.” (Quran, Surah Maidah) Nothing can be added or subtracted to Islam after this proclamation. Allah says in the Quran:
“And hold fast, all of you together, by the Rope of Allah and be not divided amongst yourselves.” (Quran)