Buck is a well-intentioned, albeit somewhat broad, documentary about a real life "horse whisperer." It should be noted that Buck Brannaman doesn't whisper so much as he goes about his business in a quiet, sincere manner. The fact that he helped Robert Redford on the set of Horse Whisperer is just icing on the cake, bonus bona fides, merely reaffirming what our eyes and ears already tell us about Buck's level of expertise.
One running theme on the origins of excellence seems to be the early childhood trauma angle. There's something about exposing a young psyche to abuse or instability that causes them to excel in certain areas (horse training, chess, painting) while struggling with others (shyness, trust issues). Buck embodies that struggle: as a youngster he faced terrible beatings at the hands of his father. That Buck chose another path -- gentleness and confidence -- speaks to the character of the man.
The documentary is comprised of a look at Buck's training classes, where he takes on different levels of ability and molds them to their horse, and interviews with Buck and his family and friends. Buck's methods are laudable and logical, he never "breaks" a horse, and he generally finds fault with the human component of the relationship when things are going poorly. He works with a wide array of horses, from colts taking on their first rider, to dressage equines simply looking for a leg up. The rich and poor come to visit Buck, because he's as gifted in the horse ring as they come.
The movie also highlights Buck's calf-roping abilities, a passion he shares with his teenage daughter. These relationships are of the stoic Western sort, with not much in the way of bluster. Buck himself is plenty introspective, but he comes off as a largely "live and let live" type of man ... so long as you're treating your horse right. But his corrections, while firm, never rise to the level of mean or loud.
This would be the perfect documentary for any young rider, or heck, anyone looking for a leadership style that's full of results and light on pomp. Buck exudes a quiet confidence, and it's interesting to see how he came upon it. In the end, Buck isn't really about horse training at all, but rather about a remarkable gentleman who survived childhood horror and made good.