There are a lot of people that'll go out of their way to deny points of history or give misleading historical statements. On the History Subreddits, moderators simply delete comments promoting the "Lost Cause" myth, genocide denial, or Hitler/Stalin apologia. What about outside of Reddit where moderators don't exist to silence such comments and where they can potentially get onto major media outlets to spread falsehoods?
There is always more that can be said on this topic, and it's a really important one, but you might like to start by reading this previous threads on the subject of how AskHistorians handles it. They do touch a bit on how many Historians handle it as well.
Monday Methods: American Indian Genocide Denial and how to combat it by /u/Snapshot52.
and Monday Methods: Holocaust Denial and how to combat it by /u/commiespaceinvader.