Right... my current summary on this:
Salt burns.... but if you handle the burning, there will be peace
Light shines and exposes the darkness... but if you remain then you walk in the light
The Church wants to remain in the world and not be salt (be compromised instead of pure) - most clearly seen in Lot's wife.
To live like salt means to live as though the world is going to be judged. period.
The Church even if it wants to be pure - it often does not want to be visibly - because then we get in trouble. To live like light is to shine into someone's life so that they are set free in the midst of a world that condemns them - e.g. John 8