There are numerous denominations within Christianity with slightly different “takes” on faith matters. But as long as certain non-negotiable ideas are included in each denomination’s program, they get along fine with all other Christian denominations.

In Islam, it’s different. Sometimes, there is all-out war between Islamic sects, and ugly accusations that other sects have things all wrong and their adherents won’t go to heaven.

Here’s a good article explaining the basis for the many sects within Islam and why they clash:

https://www.dawn.com/news/1035023

 

Differences between Sunni and Shia Muslims:

http://www.discoverthenetworks.org/viewSubCategory.asp?id=754

 

Salafism vs. Sufism:

https://www.quora.com/What-do-Sunni-and-Shia-have-to-do-with-Salafi-and-Sufi

 

Reports: Ultra-conservative Wahhabi Muslim ideology (Salafism) is being spread in American mosques through an estimated $100 billion investment by the Saudi monarchy:

http://thehill.com/blogs/congress-blog/foreign-policy/292188-no-saudi-money-for-american-mosques

 

The Wahhabi sect of Islam is said to be the source of an estimated 80% of the radicalization in American mosques:

http://www.jpost.com/International/Expert-Saudis-have-radicalized-80-percent-of-US-mosques

 

Saudi money goes to build mega-mosques in the U.S., and then, following the adage “He who pays the piper calls the tune,” it is radical jihadi-style Wahhabi content that is preached and taught inside those mosques:

http://www.huffingtonpost.com/dr-yousaf-butt-/saudi-wahhabism-islam-terrorism_b_6501916.html