I flagged the holocaust-denying post Man who claimed to have escaped Auschwitz admits he lied for years as offensive. The flag was declined, with the message
declined - This is a Politics Q&A site. We should be able to discuss the Holocaust without getting so easily offended.
There's plenty of other sites on the internet which allow people to engage in holocaust denial, but there's no need for this garbage and hate speech on Stack Exchange. We're not an "anything goes" website, and we don't claim to be one. It's one where people post factual questions and get factual answers. It's not for posting absolute nonsense as fact, let alone when it's hate speech.
Related question: Are antisemitic conspiracy theories against policy?