Does Scripture Support a Christian Church Joining in Worship Services with an LDS Church?

Questions about whether there’s Scripture to support a Christian church joining in worship services with an LDS church, whether it’s a genetic fallacy to say we shouldn’t sing any songs created by bands from NAR churches, and whether it’s a sin not to fast. Is there any Scripture that would support a Christian church joining in worship services with an LDS church? How would you handle this situation if it were happening in your small community? Is it a genetic fallacy to say we shouldn’t sing any songs created by bands from NAR churches, even if they’re biblically sound? Is it a sin not to fast?