"Christianity is just a crutch."
In other words, the person is fallaciously inferring that the origin of a Christian's belief simply stems from his/her dependency on a safety mechanism or a support system. But as stated in the prior post, the origin or how one comes to believe in something does not necessarily prove or disprove the validity of such a belief...to make a claim that "Christianity is a crutch" is totally irrelevant to whether or not Christianity is true, and simply shows that the person who makes the claim does not have a clue about logic or rationality.
So once again, take a tactical approach to turn this on the atheist or whoever makes this fallacious claim...here is a great way to do it, from Greg Koukl, (author of Tactics: A Game Plan For Discussing Your Christian Convictions).
"Some say Christianity is just a crutch. But let's turn the question on its edge for a moment. Is atheism an emotional crutch, wishful thinking? The ax cuts both ways. Perhaps atheists are rejecting God because they've had a bad relationship with their father. Instead of inventing God, have atheists invented non-God? Have they invented atheism to escape some of the frightening implications of God's existence? Think about it."
