McDonalds wants out because it is a brand that is built on an image of wholesomeness, if not healthiness.
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The overwhelming public image of the IOC is now corruption.  The association with the IOC is damaging McDonalds.  In terms of public image, they might as well be sponsoring the Mafia.
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Time to re-watch some old films.
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Start with Olympia by Leni Riefenstahl.  The opening of that work is still one of the most brilliant essays on human athleticism ever recorded on film.
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Finish with Chariots of Fire.