The difference between pigs and other domestic meat animals is that they are omnivores. Nothing to do with what they roll in.
We tend not to eat animals that are omnivores or carnivores as they pose ore risks for parasites and diseases that can cross over or the accumulation of toxins higher up the food chain you go.
Same with the bottom feeding sea food that is barred.
Think of the CJD crisis caused by feeding animal products to herbivores.
Pigs bred in the UK are safe from tapeworm etc and by law cannot be fed 'swill' or meat products and so are safe from the risks of the olden days in which these precautions were developed. But culture and belief are deeply ingrained and if something has always been 'unclean' it is very hard to shift that feeling.
And it is the same, presumably, with communities who circumcise.
But that doesn't mean it is OK to carry on such customs.