Holocaust denial, or the belief or assertion the Holocaust did not happen or was greatly exaggerated, is perhaps the most prominent antisemitic conspiracy theory out there.
The event, which was the genocide of European Jews during World War II, cost 6 million lives, not including the lives of millions of others, including ethnic Poles, the Roma, the disabled and gay men, who were persecuted under the Nazi regime.
There is no doubt the Holocaust took place, so what would an "opposing view" of it entail?
That's what's mired the Carroll Independent School District in Southlake, Texas, in controversy this past week, after a top administrator advised teachers to present "opposing" viewpoints if they're going to assign books about the Holocaust.
Gina Peddy, the Carroll school district's executive director of curriculum and instruction, made the remarks during a training session on which books teachers can have in classroom libraries.
A Carroll staff member secretly recorded the training and shared the audio with NBC News.