"What is the dignity of a human being?" and "Who is a human being?" are the two questions that fundamentally undermine a racist. It's quite possible that many racists hold their opinions out of ignorance rather than malice so an open debate is an opportunity for meeting someone in dialogue and remedying their ignorance. Those who are exposed to the truth and reject it pass over into malice and those people are their own worst enemy: leaving them in their self-inflicted echo chamber of rage is the worst possible fate that could befall them. It's not what I hope for racists, but I do pity those who end up in such a state.