Presumably the goal is to encourage people who lack awareness about issues surrounding racism and sexism to both become aware and to actually care about these problems. And to change their behavior, to the extent that it should change.
Unnecessarily attacking, humiliating, or embarrassing a person who is willfully admitting their own ignorance and seeking a better understanding of the situation is so obviously counterproductive that I can't believe I'm having to write this comment. This is not the way to win people to your side — in fact, it's completely the opposite. Doing so only causes both sides to become more firmly entrenched in their beliefs and less likely to try and discuss the issue further. By giving them a positive experience, you not only increase the likelihood of them seriously considering your arguments, but you also open the door for them to come back to the table for discussion again, even if you didn't win them over the first time around.