Why were the Japanese offended by the 1957 movie, The Bridge on the River Kwai?

This bridge was immortalised by Pierre Boulle in his book and the film based on it, The Bridge on the River Kwai. However, there are many who point out that both Boulle's story and the film based on it were utterly unrealistic and do not show how bad the conditions and treatment of prisoners were. On the part of the Japanese, many resented the movie's depiction that their engineers' capabilities were inferior to those of British engineers. In fact, Japanese engineers had been surveying the route of the railway since 1937 and they were highly organized. The Japanese also accused the film's "glorification of the superiority of Western civilization" because the British in the film were able to build a bridge that the Japanese could not.