Great piece from an Aussie on the symbiotic relationship between the Left and Islam. As the map below indicates, Christianity's greatest threats have been from Islam and Leftism, here shown in red (communism). Other less virulent forms of leftism vex the Church today, but as James Kalb correctly observes there are increasing indications that things will get worse under them in Europe and the Anglosphere. The spread of Christianity on the map is shown in white, but we do not see this threat depicted here.
My own belief is that, on the spiritual level, Leftism is a virulent form of Antichristianity that hates Christ and His Church so much that it has happily joined ranks with Islam, even if this means the destruction of its liberal states down the road. That is, it's hatred is so intense that it will gladly commit suicide in order to effect a homicide of the object of its hate. It is nihilistic to the core.
Don't neglect to read this important article.
The Spread of the Gospel from Western Conservatory on Vimeo.