Left-wingers aren't known to be friendly to religion or care about Gods.
If we strip religions down to rational level they're just ideologies and doctrines. Under this view, the most similar to Islam is Nazism, both blame Jews for everything, both are supremacist, both are totalitarian...
So... what are those guys defending?! What supporting arguments do they have?! Ad populum, because they are too many?!
I think it's a rather functional than ideological "love". Probably they see muslims and mass immigration as a good tool to finish communities with historical christian roots off. Also, muslims are useful tools against whites, especially in Europe (because of the slow reproduction rate of the indigenous people). As a plus immigrants more likely to support leftist/liberal than conservatives parties.