Where there is a will, there's often a way. Several prominent conservatives don't agree with the premise that Islam (in general) and the American left's version of Marxism are incompatible. They both want to destroy America and Israel. If they succeed the world is theirs.
David Horowitz, Unholy Alliance: Radical Islam and the American Left, 2004 -
Andrew McCarthy, The Grand Jihad: How Islam and the Left Sabotage America, 2010
“Radical Islam’s Alliance with the Socialist Left” a section of DiscovertheNetworks.org
The Sunni radicals and the Marxists may work with each other on occasion, however when it comes to the very basic beliefs of each they are quite divergent.
Think about how western marxists, like Bill Ayers, thinks about women and then contrast that with how the Sunni's treat their women.
Think about what it would be like if there was a Sunni caliphate in charge of this country. Do you think they would stand for all the gays acting on their "rights."
They are so far apart that even if they spend all their time taking over the world together, in the end they would kill each other.