Having been called "a mercenary" and a "baby-killer" I've always liked this poem by A. E. Housman:

Epitaph on an Army of Mercenaries

These, in the day when heaven was falling,
The hour when earth's foundations fled,
Followed their mercenary calling,
And took their wages, and are dead.

Their shoulders held the sky suspended;
They stood, and earth's foundations stay;
What God abandoned, these defended,
And saved the sum of things for pay.