This is quite bothering me for a while because of my lack of ability to summarise the history of the Holocaust into short points. Moreover, I am having a hard time explaining the truth about the Holocaust to my friend. So, I need your help to articulate and break it down into points adding sources in the end accordingly.
There's an awesome post by u/commiespaceinvader on the topic of Holocaust denial and how to answer to it. Maybe he or other want to add further points, but maybe try that very thorough post as a starting point.
If you live in the States, DC and Chicago have two places worth taking them. Anyone who sets foot in one of the locales and still doesn’t acknowledge the Holocaust isn’t worth arguing with.