True, at least in his later years.
... leading in large part to a worldwide Depression.
Maybe not so true. Keynes changed his views during the Depression. He was a free trader before that.
The delusional “progressive” economist Paul Krugman is another protectionist
That's also true. But not true of most recent Democrat presidents, who were strongly in favor of free trade and foreign trade agreements.
Not really. They paid lip service to free trade. What they were for is managed trade, a la NAFTA.