You could, I suppose, always respond with a fake catechism style question and answer, thus:
Q. Why did God make alcohol, tobacco, and marijuana?
A. God made alcohol, tobacco, and marijuana to see if men were stupid enough to use and abuse them.
If they’re stoned enough, tell them it really is in the catechism, and you heard it from a nun. That ought to shake them up a little bit on some level!