If the Klansman was not a murderer and they were just ignorant, then yes. However, if this person has a history of assault and racially motivated lynching, then no I don't want this person running our country, because they would have the power to terrorize unwanted people. Same with a war criminal. I would not want a war criminal running our country.
I believe it would be useful to ban former members of the Ku Klux Klan from participating in politics, but I believe as long as their history is properly released and reported by the media, that will be sufficient. From my perspective anyone who found the Ku Klux Klan useful as an organization is not useful to society as a whole.
This whole debate is on FORMER members. This leads to the thought that they are no longer bigots or radical racists. They shouldn't be banned. In fact, they can provide a point of view as a member of a KKK because of this history. This aids in the whole nation coming together to make decisions that are well received by diversity. As a democratic government, they won't be elected anyway.
Ku Klux Klan members should not be banned from politics. In fact, this applies to both current, past, or future Klan members. They, just like every other American citizen is invited into the political forum. That is what makes this country great. Regardless of how crazy or misguided your ideas may be, someone will at least listen to your view, and you have the right to be heard. Every citizen has this right. Without this right, guaranteed by the 1st amendment of the US Constitution, We would be just as oppressive as those in the Communist or Socialist regimes around the world. However, you are not guaranteed that your opinion will be well received or respected. That is entirely based on your ability to persuade.
Of course, anyone in the United States who is an American citizen has the right to participate in its political system. While no one from the Ku Klux Klan should ever be elected because of its hate rhetoric, a former member of the organization might very well be a reformed member and that would be a helpful position.
While the views of former KKK members are distasteful to most, we should not ban them from participating in politics. It is better to have offensive views debated and countered in the public sphere than to have them be operating outside of the public eye. When they are out in public they also can be countered with more rational viewpoints.
I believe the Klu Klux Klan is a terrible orginization and should have never been formed. However who are we to judge someone else's freedom. Someone can believe what they want and it is their right. So many things could go wrong here. If we don't allow them to run who is it to stop the next orginization others don't like have that right taking away.