Surely it is more akin to going into a shop that has a sign in the window saying Free Coffee for all Seniors and being a teenager asking for a free coffee. If the shopkeeper then gives you a free coffee can they turn around later and say you stole it because you were not targeted for this offer even though they are the ones who control the handing out of the free coffee. It doesn't quite sound like stealing to me.
I can't go and take the points, IHG has total control over their dispensation. They just choose not to exercise that control very well.