I don't think we could say that Ball exemplified "realpolitik." He certainly was right about the Vietnam War, and he correctly (some scholars say "presciently") predicted the negative consequences of escalating the conflict. Calling for the United States to not go to war, however, aligned with Ball's values, and so this cannot be said to be a strict example of realpolitik.

On the other hand, there is at least one example of Ball embracing his values even when it did not serve the real interests of the United States. After the Soviet invasion of Czechoslovakia in 1968, George Ball (then ambassador to the UN) gave two impassioned speeches to the UN General Assembly. He called the Soviet excuses for the invasion "an obvious fraud" and referred to the invasion as "rape," and he celebrate the democratic history of Czechoslovakia, among other things. Now, obviously the United States was going to protest the invasion in the UN as a matter of course, but behind the scenes, Lyndon Johnson immediately began to attempt to repair Soviet-American relations in the hopes of realizing an arms reduction agreement before the end of his term. Ball's two impassioned speeches went beyond anything that the administration wast trying to do at the time. Perhaps it was all just for show, but in this case, it certainly seems as if Johnson exhibited something closer to realpolitik than Ball.

Ball's speeches can be found in the State Department's Bulletin (available at many university libraries), dated September 9, 1968, pages 263-274.