Ambivalent removal, eh? Now what in the world does that mean? Well, the word ambivalent means that you really aren't sure how you feel about something, and the word "removal" in this sense means that Yeats distances himself from all of the patriotic rah-rah emotions that fuelled the Easter Uprising.
And yeah, this is pretty typical of Yeats. Yeats tends to stand back from the world as a poetic observer. Then when history starts being made and guns start going off, Yeats keeps his distance and writes poetry, like, say, this little gem. Part of you wants to respect him for it; the other part wants him to stop being such a wimp and pick a side.