During the second stanza of this poem, Yeats goes through a short list of some of the people he knew who fought in the Easter Uprising and who were either jailed for life or executed. It's not totally clear whether he admires them or doesn't care about them. But one thing for sure is that he feels like he needs to write about them, even if he isn't sure why.
Lines 17-23: Yeats mentions a woman who helped with the Uprising, and it's likely he's talking about the Countess Constance Markievicz. But it's not like he's painting a flattering portrait of her. He basically says she used to be beautiful, but now her days in politics have made her voice shrill. Oh yeah, and he says that her political life comes from a sense of "ignorant good will." Sheesh, tell us what you really think, Yeats.
Lines 24-30: Yeats goes on to talk about some dudes he seems to have had a bit more respect for than the Countess. First, he talks about some guy who founded a boys' school, and he's probably talking here about a guy named Padraic Pearse, who was also a poet. On top of that, he mentions a guy who helped Pearse, who is probably Thomas MacDonagh, a poet and dramatist. Yeats even suggests that MacDonagh could have been half decent if he hadn't gotten himself involved with the uprising.
Lines 31-35: Finally, Yeats mentions a guy whom he didn't like at all. Basically, he found this last guy really cocky and rude. He's no doubt talking about a guy named Major John MacBride, who was the husband of a woman Yeats was in love with. So yeah, Yeats had some ulterior motives on this one. But still, he admits that he wants to include MacBride in the poem because like him or not, MacBride gave his life to the cause of Irish freedom.
Lines 74-77: At the end of the poem, Yeats throws down the names of the dead fighters he's been talking about in this poem. He's not sure if he totally agrees with what they did, but he can admit that they've done something he would never be capable of, which is die for a political cause.