Don't mention the war

I'm preaching for the Friends at the Advent at their Halloween Mass on Friday night. We're using the All Saints readings, for obvious reasons, and I have only one request from the celebrant: "Mention U2." I find that quite funny, since sermon preparation for me would normally be more likely to involve the opposite effort: don't mention U2. And now that I've started working on the sermon, I find it even funnier... because I cannot think of anything U2-related to say about All Saints.