On a broader scale, the marriage of far left and islam are not from some love of shared values. Its from the love of shared enemy, capitalism and western civilization.
I'm not saying, I'm better, I'm pretty apathetic. But I don't get it.
Slaves as a term isn't as relevant today as it was centuries ago, but still it captures the idea of a class of "oppressed and powerless" people well.
In an extreme twist of irony however, both Christianity and Judaism are religions born from slaves, hence the emphasis on classic liberal values (love thy neighbor as thyself). Islam however is not a slave religion, and was born from power, on the other end of the spectrum (kill non-believers who don't convert)