If they did, it would have cancelled out what they believe faster than Christianity. You may be greeted with a humbling silence or diversion to another issue. Some say the Resurrection never happened. Josh McDowell's Volumes Evidence that Demands a Verdict offer compelling quotes from various non-Christians sources during this time that validate the Resurrection. Some say that the church is about nothing.
Every church is different.
Alot of those who make this statement aren't doing anything themsleves. Some say Jesus Christ is a myth. Some say he is not the begotten Son of God. At the root of this issue is faith. But faith requires bringing yourself into submission to God and his precepts.