Your definition of mainstream culture is now clear.  It can be defined as anything but Muslim.  It is clear because your constraints are designed to exclude only Muslims.  I also have no idea where you get the notion that I favor the melting pot.  I don't.  I acknowledge that a melting pot scenario is inevitable where cultures intermix, but I am not afraid of cultures that challenge some of my preconceived norms and values and am open to learning/adopting from other cultures and societies as well.  After all, culture is nothing more than a social construct of our own devising.  Static cultures tend to die, while open cultures tend to grow and thrive.  Yes, we can even grown by open our minds to concepts from your boogeyman, the muslim peoples of the world.