I belong to a recorder group and we regularly perform in churches. Although I am not a religious person, it doesn't give me any problems.

Mostly we are performing music as part of a concert of essentially secular music but I have been involved in performing as part of a service.

While I agree with you about the problems of extreme beliefs and we are seeing the consequences of this too often in the world just now, I am happy to support people on a personal level and to respect their beliefs.

On a purely practical level, churches often have excellent acoustics and there is something magical about performing a renaissance fantasy in the type of acoustic you often get in a church, especially an old one.