Hi there -- while you wait for a precise count, you may also be interested in these older threads by u/snapshot52 about American Indian genocide denialism and how to combat it:

https://www.reddit.com/r/AskHistorians/comments/6kywre/monday_methods_american_indian_genocide_denial/

and

https://www.reddit.com/r/AskHistorians/comments/6mg3j3/monday_methods_american_indian_genocide_denial/