Invictus by William Ernest Henley happens to be one of the handful of classic poems that can be considered genuinely popular. The sort of poetry mavens who like John Donne and William Butler Yeats tend to look down on it, but it has made quite an impression on the popular consciousness. It is very frequently quoted and likely to show up almost anywhere. There is, for instance, a sometimes hilarious anthology of pieces spoofing literary criticism called the "The Overwrought Urn" by Charles Kaplan. Many of the pieces are about very familiar works, and inevitably one of the pieces is about Invictus.
Charles Johnson of the pioneering blog Little Green Footballs notes in a recent post that someone in the comments thread at Michelle Malkin's blog has posted Invictus, and he informs us that the poem was "the final statement of Timothy McVeigh" as if that is the poem's principle claim to fame and as if it quoting it marks one as some sort of political extremist (or whatever point Charles thinks he is making). He needn't have bothered posting a photo of McVeigh's handwritten copy of the poem. McVeigh's use of the poem is simply one of the many examples of the poem's tendency to show up in odd places--now including LGF.