The Russian Candidate is correct in saying that some countries, Japan and China for example, are currency manipulators and that Germany is essentially doing the same thing through the Euro. In effect they are not letting market forces balance out world trade which would in the long run make their goods pricier in US markets.

Investing the profits of their trade in the US might be a tradeoff but funding the US government deficit is not in my opinion what Keynes had in mind since it does not lead to a rebalancing of world trade.

In the long run the costs of production in all countries should balance out such that no nation has an advantage. The balancing comes through appreciation/depreciation of currencies. That is not happening because of currency manipulation.