dmigtysolomon may I ask you one thing. I know many filipino and filipina claims to be Christian has spouse back in Philipines and have partners here. Is this is right as per your belief?
Regarding polygamy, It is allowed by Almighty thus we are not the one to make it Haram.
The one who doesn't follow the Teaching of Islam is already out of Islam. No one has to expel him. One more thing, Islam is not a society or union to expel some one. It is a way of life and the one who don't follow is already away from the system.