Actually, it’s about the massacre of Glencoe. Macaulay is trying to figure out what could have motivated John Dalyrmple, the Master of Stair, to order a mass murder in the name of William III, Macaulay’s hero:
The most probable conjecture is that he was actuated by an inordinate, an unscrupulous, a remorseless zeal for what seemed to him to be the interest of the state. This explanation may startle those who have not considered how large a proportion of the blackest crimes recorded in history is to be ascribed to ill regulated public spirit.
We daily see men do for their party, for their sect, for their country, for their favourite schemes of political and social reform, what they would not do to enrich or to avenge themselves.
At a temptation directly addressed to our private cupidity or to our private animosity, whatever virtue we have takes the alarm. But, virtue itself may contribute to the fall of him who imagines that it is in his power, by violating some general rule of morality, to confer an important benefit on a church, on a commonwealth, on mankind.
He silences the remonstrances of conscience, and hardens his heart against the most touching spectacles of misery, by repeating to himself that his intentions are pure, that his objects are noble, that he is doing a little evil for the sake of a great good. By degrees he comes altogether to forget the turpitude of the means in the excellence of the end, and at length perpetrates without one internal twinge acts which would shock a buccaneer.
Glencoe was three hundred years ago. Some things never change.