Taking what belongs to someone else and choosing how it will be used without the owner's consent is the purest essence of theft. It makes no difference whatsoever that—according to your own values and preferences, not theirs—you think the benefit outweighs the cost. You don't get to make that choice for them. Regardless of how the money is used the very fact that their choice was taken away is harmful in itself, and only by returning what was stolen—plus compensation for lost time and opportunities—can the victim be made whole.