Do we know if Corbin has actually denied the Holocaust ? - No, he hasn't done that. Corbyn accepts that the Holocaust happened and that it was a bad thing.
But there are still the issues of his manifest double standards and his claim to be for peace.
I've already covered his double standards to a reasonable degree, so now it's worth talking about his claims that he is and always has been 'for peace'.
So, in the name of peace, Corbyn had a close association with Deir Yassin ... who, being Holocaust deniers, are anti-Semitic. Recall, too, that he attended a ceremony in Tunisia which celebrated and commemorated the lives of a couple of dead Palestinian terrorists. He also is on video calling Hamas and Hezbollah his 'friends' (but he's never called the Israeli government 'friends'). In fairness to Corbyn, he apparently now does regret using the term 'friends' when referring to Hamas and Hezbollah.
And now for a quick aside, but one that's relevant to the point I'm trying to make ...
Corbyn claims that his whole stance on Northern Ireland was 'for peace', too. My memory isn't 100% on this, but at the height of The Troubles, he apparently invited leaders either from Sinn Fein or the IRA to Parliament. Corbyn likes to revise history and claim he was neutral and for peace, but his view at the time was for a united Ireland. That's the same view as the IRA, incidentally. So that's his claim for neutrality out the window.
In that full interview I posted above, Andrew Neil put to him this hypothetical scenario:
Our Special Forces have got the next ISIS leader cornered and are awaiting instructions. Would you give the order to take him out?
And Corbyn couldn't say 'yes'.
Have you noticed a pattern emerging?
Well, I have - the pattern is that Corbyn sides with the UK's enemies. In short, he is either outright anti-UK or his idea for Britain is so radical, so batsh*t crazy that it goes completely against the vast majority of the UK electorate's wishes.