The rise of Islamo-fascism with the intent of conquering the world and imposing retrograde Islam on the rest of the world. From ISIS to Boko Haram to Al Shabab the groups imposing Shariah law in Aceh province in Indonesia and fighting to do the same in the Philippines.
When these groups take over, women lose all rights (forced marriage, sex slavery by some of these groups, worth half of men in inheritance and courts, forced veiling, often denied any secular education). And as you see with the Muslim Brotherhood that took over in Egypt before the military coup, they end birth control in the attempt to drive up birth rates.
That's on top of their open executions of atheists and homosexuals. (Bangladesh and Pakistan, for example, won't investigate the dozens of atheist murdered in 2015 because it was considered appropriate per the Koran.)
Multiculturalism that tolerates intolerant cultures results in setting back human rights centuries. And this is true even for Muslims coming to the West. See the Rotherham rape scandal where police though it worse to be called racist than round up Pakistani Muslim rape gangs targeting under-aged white girls, over 1400 girls raped. Or the Taharush across the EU on New Years 2016, and police actively suppressed the news and ignored reports because it was considered more important to ensure positive portrayal of Muslim migrants than deal with public rapes and groping.