Stonehenge has influenced many groups over the eons, as it was intended to do. The Druids did not build Stonehenge, but they incorporated it into their rituals. Thus, history tends to credit them with erecting Stonehenge. Religious rituals, or those semi-religious rituals that form in highly structured social groups, are put into place to control the membership and give them outlets for emotions that would otherwise be disruptive. Emotions such as jealousy or fear can scatter a membership, but if given an outlet that tends to support the groups goal, build and support the group rather then tear it apart.
Human sacrifices are one such ritual, as the sacrificed one acts as a scapegoat, becoming a symbol for whatever has caused rage in the membership. The leaders, of course, select someone they wish to get rid of, a troublemaker or an independent thinker. Stonehenge by its very shape implies sacrifice, but it did not cause this behavior in the Druids, as using scapegoats and rituals involving sacrifice occur in all cultures and all parts of the world. The close proximity to such an edifice as Stonehenge to any sacrificial rituals would naturally align into a mental association over time, and this is what occurred - a coincidence, made into cause and effect by historians.