In the U.S. a Christian cathedral allowed a Muslim to give the Athaan from inside the church.

Answer

Harmonious existence with shaitaan is haraam. The Qur'aan explicitly declares that shaitaan is our avowed enemy. This interfaith kufr act enacted to dupe stupid people is an inspiration and stunt of shaitaan. Giving Athaan in a Christian Church is a ploy of shaitaan. Shaitaan misleads people under Deeni guise. Muslims who become entrapped in such shaitaani plots may even lose their Imaan. With such subtle tricks does shaitaan make kufr and shirk religions acceptable to Muslims of weak Imaan. Such Muslims may even become murtad. The Shaitaani ploys of the interfaith movement are a gradual creeping disease. By degrees is the Imaan of weak Muslims desensitized and corrupted with their association with religions of kufr. The Qur'aan Majeed repeatedly prohibits Muslims from befriending the Yahood and Nasaara. Friendship with them makes their religions acceptable to Muslims. The 'benefits' of this dubious, haraam 'athaan' delivered in the church are hallucinatory. It is all a trap of shaitaan.