I'm sure that it did help the cause to a certain extent but even today there's a ton of racism. It's sad that people can't look at someone without noticing their color of skin first. We as a nation need to rise above racism and look at a person's heart and character.
The fiercely committed Kennedy decided to infiltrate the group and expose its secrets. He was quite successful in this—for example, he learned that when a traveling Klan member wanted to find other Klansmen in an unfamiliar part of the country, he would ask for a “Mr. Ayak”—“Ayak” standing for “Are You a Klansman?” The desired response was “Yes, and I also know a Mr. Akai”—“A Klansman Am I.”
While entertainment media is a useful platform to address serious issues, such as racism and sexism, it cannot "take down" or dismantle these organizations. Kennedy was, however, successful in providing representation to the racial minority. He also brought a lot of the hidden ugliness of the hate group to light, which is a positive thing. More must be done, however: it is the people in the real world who make these changes.
No, Kennedy was not successful in taking down the KKK with Klan related episodes of Superman. A great deal of effort and government time was spent on diminishing the presence of the KKK in America. Klan-related episodes of Superman may have been an effective strategy at getting the message out, however, this cannot be credited for taking down the KKK.