To answer your question: 1) Christianity doesn't advocate for the killing of non-Christians, forcing women to dress in burquas, throwing gays off of rooftops, etc....; 2) There is a difference between government forcing people by law to adhere to a given religion, and government officials subject to election, exhibiting a preference for the tenets of a given religion.  Sharia makes no bones about its desire to make religious law through the government.