N. Korea sold their technology to Pakistan It seems to have been much more he other way round.
.........................................

"...show how a defensive system that can only shoot down missiles that are being used OFFENSIVELY is threatening..."

If a potential enemy manages to install really effective defences, this reduces the deterrent effect of your own weapons, and in principal puts the other side in a position to use its own weapons without fear of effective retaliation.

Once again: "Armour is purely defensive too. For example, on a tank."