Well, speaking from experience there was no problem with some of the nasties that you mention. Also, there are PLENTY of nerve endings in the anus for both men and women-- men have the added benefit of the prostate, whereas personally it stimulates my g-spot, just from the other side of the tissue... Done in a loving (and not scary, forceful, squeal like a pig fashion) it was one of the most amazing sex encounters for both myself and my s/o.

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I am certain of nothing but the holiness of the heart's affections and the truth of imagination. What the imagination seizes as beauty must be truth - whether it existed before or not.
-John Keats