we're not discussing you
The interview was recorded only after Lanzmann pretended to be a sympathetic journalist writing about Treblinka--wanting neutrally to get the facts.
Although it seems that Lanzmann is using his razor-sharp irony here - part of his lie to get in to see an infamous Treblinka guard (he told him he didn't want to focus on the individual crimes but wanted to get a precise sense of the camp) - actually in the end I think it's true that Lanzmann isn't interested in Suchomel. He wants to get Suchomel to help him paint the broadest possible canvas - the big picture of the genocide across the landscape.
A YouTube video version of this scene.