How is it preventing oversupply? It is just a re-seller of that supply, if it consumes nothing productively, it is just an intermediary middleman centralizing foreign counterparty risk at the expense of the national treasury? It merely adds waste to the economic system in which it operates.
The ex-im bank is able to release the supply at a slower pace then the original producer would be able to. The producer would have to pay it's employers and it's suppliers; if it's buyer is not able to pay then it would need to rush it's now unsold goods to the market in order for it to pay it's bills.
Then why (over)claim that it reduces supply when you clearly state it doesn't do anything more than put it on a shelf to rot and become obsolete, just like it would on the producer's shelf, and perhaps ultimately be sold? This is not reducing supply, only productive use does that. This is not a public good, it is the opposite, a public taking.
It is a politically controlled market distortion at public expense for private benefit, subject to lobbyist influence and plain corruption. Government ought not be in this business, it is wrong and a misuse of power.
I was in the "What is it?" / "I don't care" camp until all these ExIm apologists came along with these mealy-mouthed justifications. The more they write, the more reprehensible it seems. Should just stop and hope that folks don't see it for what it is. The more you explain, the worse it appears.
Not much patience for all this lipstick on a pig.
Having too much supply on the market at one time would mean that the price of the subject good permanently be lowered.
You also need to remember that the ex/im bank does not work for free. They do charge something in exchange for guaranteeing payment. Most of their opponents say they do not price risk appropriately but this is a separate argument.