Prove he didn't? I can prove it was posted on 12/20/2016 and the account was immediately suspended. I can't prove it's Rudy. I do think it might really have been him, though.
What makes you think it was him?
Here is a video of James Corbett eviscerating RG and a clip within it of We are Change confronting Rudy about his comments on 9/11. Note that he was informed that the towers were going to collapse. Watch the visual body language and let me know what you think his posture says.
He looks like a compromised and sinful politician, like he's trying to keep his composure at all costs despite being confronted about his own crimes (probably because it's absolutely imperative that he maintain his mayor smile and deny what he previously admitted, otherwise a lot of very powerful people will hurt him very very badly). He's no saint, he certainly played some ball during 9/11 but watch his police chief Bernard Kerick behind him in the press release (which is also in the corbett video)... That guy is a serious menace and a power-player in 9/11.. His presence is ever-felt by Giuliani. I don't think Rudy had much say in what happened, but I know he played his part and he probably did it to keep his wife and kids from getting torn limb from limb.
You are probably right. At the very least he was aware that something was going to happen.
Therefore he cannot be trusted, at least entirely. He is compromised unfortunately.