More than anything, Yeats' "Leda and the Swan" is filled to the brim with contradiction and subtlety. While on its surface the poem presents the violent bestial rape of Leda by the disguised Zeus, the intricate deliberate language used creates a series of complex dichotomies -- power vs. weakness, control vs. submission, love vs. violence, beauty vs. ugliness, human vs. god, the acceptable vs. the disturbing, etc. These complexities are used both directly and indirectly to reflect the similar complexity of the then-current sociopolitical climate, especially regarding the state of women and their rights. Being as involved in politics as he was, W.B. Yeats no doubt could not wholly ignore the rising call to action in favor of women's rights, but this was a subject that was still highly controversial during the First Wave Feminist Movement. In order to address the issue, Yeats thus chose a well-known subject and story -- the myth of Leda and the swan -- and turned it around on itself, placing Leda in the position of a victim with whom the reader is meant to sympathize. In fact, Yeats' contemporary Aldous Huxley wrote a similar version of the myth, published four years before.
Yeats does not take an evident stand on the issue of women's rights, nor on the issue of the morality of the Leda and the swan's coupling. His contradictory language well reflects this, and this is because that is simply not the point. We as readers are not meant to read into Yeats' intentions; instead, we must make up our own minds about who is deserving of power or sympathy, pity or control. There is evidence enough for both sides of the spectrum, and so the problem lies primarily in the individual reader and interpreter of these presented "facts" in poetical format.
The poem becomes something similar to Frank R. Stockton's allegorical "The Lady, or the Tiger?" (1882), which presents the reader with an unsolvable problem based purely on the reader's affections and psychology. Yeats, too, is presenting us with a question, literally in the final lines as well as figuratively: what is wrong with this picture? Depending on the the reader, the poem depicts a woman put in her place, the vile molestation of a poor defenseless girl, the physical mother of all destruction and evil, or the empowerment of a woman that would become the catalyst for the birth of the modern world through her knowing sacrifice.