[Frumanchu]

Then with a twinkle, he said, "Tell him this: If you could have created your mother and preserved her from original sin, would you? Would you?....Of course you would!
"But could you? No, you couldn't! But Jesus could and so Jesus did!"

To which I would reply: "If you could have created your sons and daughters, the brothers and sisters (and co-heirs) with your firstborn Son, and preserved them from original sin, would you? Of course you would! Could you? No, you couldn't! But God could have (according to the doctrine of the Immaculate Conception)...and DIDN'T!"

[xzins]

Exactly, a beginning of an argument.

What is wrong with addressing a teaching?

The argument is this: "As Son, Jesus would have preserved His mother from all ill."

How do you approach it?