Of course this poem is about blame: the first five words are "Why should I blame her"! The beauty of a rhetorical question like this is that you can blame her and still make it seem like you are being generous and forgiving. It's clear that the speaker has not yet resolved his complicated feelings for the woman, either on an emotional or an intellectual level. His most damning accusation is that she has stirred up political violence among people who don't know any better. But "No Second Troy" conceals as much as it reveals about the speaker's feelings. He might still be furious with the woman and her troublemaking, or maybe he has resigned himself sadly to the way things are.
Despite the speaker's accusations, Maud Gonne emerges from the poem as a sympathetic, even persecuted, figure.
The poem amounts to a total repudiation of Gonne's political tactics, even as it upholds the speaker's love for her.