Madonna going through with this is exactly (part of) the reason the pilgrims first came to America. For religious freedom and tolerance. As Americans we believe in equality to the umpteenth degree, so we always feel the need to butt in and say, "Oh what you're doing is wrong". But that's just their culture.
It would be like a foreigner coming to the US and preaching about how fascist it is for Americans to say the pledge of allegiance in school or for us to put our hands over our hearts when we hear the national anthem.
If she's going to shade followers of the Islamic faith for what she perceives as oppression against women, then I hope she speaks out about the sexism in Christianity as well.