Rather than Freud, I thought of Plato. The problem, I think, is that some want to read this as prescriptive poem, that we need to be more like the horses in their freedom or lack thereof. For me, the author's goal was to capture some essential character of horse-ness and to present it to us. This is a kind of freedom, only insofar as it is an indifference to human activity. "Hey the gate's open? Let's go see what's going on over there." The horse doesn't have any complex notions of capture or escape or goals. Its perfectly content to be a horse. I don't think there is any lesson for us humans in the horses behavior, unless it is to embrace human-ness the way that horses have embraced horse-ness.