You'll have to see "On The Waterfront" yourself to judge whether Kazan's justification is successful. I saw it several years ago and, apart from Marlon Brando's legendary I-coulda-been-a-contenda scene, I found it to be horribly melodramatic and cliched, leaving me somewhat appalled by the fact that it is recognized generally to be a classic. But, that's OK; I'm appalled by the way in which "Gone With The Wind" romanticizes the antebellum South. So I may not be your most reliable movie guide.
But it's difficult for me to accept the argument that service as a HUAC witness was any great creative spur for Kazan. He only directed nine movies after "Waterfront," only three of which--"East of Eden," "A Face in the Crowd," and "Splendor in the Grass"--are remembered today. And one of those movies was an adaptation of his own potboiler novel "The Arrangement," an attempt on Kazan's part to justify marital infidelity for the sake of destroying a life he had built and attempting to find a better one through sex with a younger, attractive woman. Perhaps the ending of the novel is the most revealing insight into Kazan's thinking: his hero admits that, when all is said and done, he still doesn't understand why he did what he did.
Similarly, I'm not sure that Kazan ever understood why he testified before HUAC when so many of his colleagues properly understood the committee's work as a direct assault not only on the First Amendment, but on the rest of the Bill of Rights as well. It assumed guilt, and demanded the production of innocence. It destroyed not only countless careers, but many lives as well. It produced no evidence, when all was said and done, of a show-business conspiracy to destroy America. Even Charlton Heston, no one's idea of a bleeding-heart liberal, described HUAC's crusade against the Constitution as "an exercise in futility."
And Kazan himself was somewhat ambivalent on the subject. In an interview many years after the release of "On The Waterfront," Kazan was quoted as saying, on the subject of his testimony, "Maybe I did wrong, probably did." The truth is that HUAC destroyed everyone who came into contact with it. It divided Hollywood into "commies" versus "finks." It destroyed the creative work of the world's premiere creative community. It created a legacy that still shadows the American film industry, even today. Perhaps it was best summed up by historian Arthur Schlesinger, Jr., in a New York Times op-ed piece written around the time Kazan got his lifetime achievement Oscar, in which he quoted blacklisted screenwriter Dalton Trumbo on the subject of the blacklist:
When you who are in your 40's or younger look back with curiosity on that dark time, as I think occasionally you should, it will do no good to search for villains or heroes or saints or devils because there were none; there were only victims.Personally, if all we got out of that dark time was "On The Waterfront," I don't think it was worth it.