Have to contradict you there,
"My Ummah will be fragmented into seventy-three (73) sects. All of them will be in Hell Fire except one sect. They (the Companions) said: Allah's Messenger, which is that? Whereupon he said: It is one to which I and my companions belong". [Tirmidhi. 171]
http://thesunnahway.wordpress.com/about/
Tolerance and unity is essential in all circumstances. Here is another Hadith, the source of which I forgot (sorry)
Support your Muslim brothers in all circumstances, even if they are Zalim. Sahabas asked "Why if they are Zalim?". Prophet (PBUH) replied: To correct and mend their ways.
You know the different sects Shia, sunni, wahabi etc?
For one thing, they all believe in and follow the 5 pillars of Islam: Imaan, Prayer, Hajj, Fasting and Charity. They all believe in Mohammad (PBUH). So, why are there differences? If you study them deeply, you'd find that the differences are over petty things. Still, these petty things are made a mole out of a hill and fight ensues due to this.
However, this does not apply to Kharijites and Ahmadi sects which are obviously non-muslims as they believe in prophets after Mohammad (PBUH) and believe in declaring "muslims as non muslims" and waging war against muslims.