Mad Cow Disease ruined the traditional enjoyment of a pot roast, since people stopped buying beef. The implication is the "the bastard" does a similar thing for sex - ie. ruins it in some way. No it's not possible to explain it fully because there's no context at all about what the bastard did.
If the sentence were "An asteroid did for the dinosaurs what mad cow disease did for the traditional pot roast" it would be easier to explain because we know what the asteroid did for (to) the dinosaurs.
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