Without reading the Book of Mormon how can you disbelievers say it is not scripture?

Some say I am gullible for believing that it was translated from gold plates that have been taken back by the Angel Moroni. They are trying to out think God who demands that we live by faith, not proofs. Shauna said that the Mormon Church is low on the food chain. How can she say that about the most active, tithe paying, chapel-building, missionarying, disaster helping church (per member) on the earth today?