Of course it can be used against him. If democrats claim he is lucid enough to be President of the USA then he was lucid enough when he said that, and damn well meant what he said. This is a guy they claim is well enough to deal with foreign leaders? Fine, then whatever comes out of his mouth is valid.
What would be hilarious is if this video of Creepy ChiCom Joe is submitted with filings of the growing election theft evidence in federal court.
Some lawyers wouldn’t do it but IMHO, it would be useful as the corporate Dem Media would go nuts.