The political left and islam are both totalitarian ideologies and have historically killed all that don’t agree with them.
I think this particular ‘left’ is a group of intellectuals who feel a kinship of sorts with the Islamist side. They seem to think that whatever exists outside of Christianity might be appealing.
Its the 21st Century’s version of the Molotov-Ribbentrop Pact.
Wish it could be framed more elegantly, but it’s essentially whats going on.
I also think that there are those particularly communist type progressives that would use whatever means necessary, include take a chance with disaster like letting the Islamic movement grow as to pressure, confuse and muddle the issues, and think that afterwords they can dominate.