Christianity can't be true because Jesus didn't return like he promised in the lifetime of his disciples. Can't really blame them - desperately grasping at straws like that. Otherwise, they'd have to bow the knew and cry out for Jesus. Mariano has written a great response to their "argument". I know it's been answered before - completely and since 2 Peter was written in the 1st Century AD, but considering that people today are still trotting out such nonsense, we still need to give them the answers even if they won't listen to those who wrote them down first. Read Mariano's article at the following link.
The “Science Club of Long Island” claims that Jesus broke His promise to return | True Freethinker