In regards to John 6:52-58 they will say (as per the Insight book)
"This is not contradicted by Jesus’ words at John 6:51-57. Jesus was not there discussing the Lord’s Evening Meal; such an arrangement was not instituted until a year later. The ‘eating’ and ‘drinking’ mentioned in this account are done in a figurative sense by exercising faith in Jesus Christ, as is indicated by verses 35 and 40."