"Probably the longest and most significant single segment cut from the series is the exposition from early in the first series about the history of the battleship Yamato in World War II. The battle in which the battleship is sunk is shown in some detail, in order to explain why the ship's hull now rests at the bottom of the sea...."
"In one sense, the extent of this cut is surprising, considering that many American viewers may not be familiar with the history of the real, historical Yamato, and would probably benefit from the exposition. However, a closer viewing of the segment reveals themes some may have found objectionable, such as the captain of the ship-portrayed as a noble warrior-tying himself to the wheel and going down with the ship. Sailors and pilots are seen sadly saluting the fall of their noble enemy, and it's possible that the sympathetic portrayal of the enemy the United States fought so hard against during World War II may have been seen as too risky by the show's American producers."
-Walter Amos, Animerica Vol.3 No.8 (p.10)-
It's certainly safe to say those underlying nerves were understandably frayed following World War II. Both sides were suffering the long term effects of a terrible war.
While certainly a very Japanese attribute, I know a few families linked to World War II veterans that would not have saluted their enemy. Some still look at the historic relationship in a much different light and context to the anime fan despite the generally positive relationship that has been forged between the two nations over the course of time. Time to heal is always essential.