Holocaust deniers are vocal about claiming the holocaust did not happen. Some claim it is best to ignore them, I believe it is best to challenge them and show they are wrong and their claims destructive.
Without answering them, people can fall for falsehoods as though it was reality. By answering them with hard cold facts, you may not change their opinion but may show others that holocaust denial is ridiculous. That the holocaust was a reality and keep them from believing in holocaust denial and revisionist history.
Often, I have found many do lack information. True, they hold onto their opinions regardless of true facts but if others see the facts presented, they may not be left to believe in revisionist history. Many did not challenge Hitler, saying he was a ridiculous corporal with silly ideas. Those silly ideas went on to ravage Europe. If we do not stand up and say "you are wrong and here's why"... then we are not standing up for what is right. We need to make our voices counted among those who will not tolerate the memory of those who died....to be forgotten.
I don't see why we should waste time and energy to convince people that are unlikely to change their minds. This was a terrible thing that did in fact happen, and whether a minority of people insist that it didn't is to me not an actual problem, it is a shame that we have people with such small brains, but it is a problem out of all problems that we should prioritize? No! Let people believe what they believe, belief doesn't change facts