Amy Alkon, author of I See Rude People, has an interesting column on porn:

It's hard to have a rational conversation about porn because people's first reaction is so often knee-jerk hysteria. I got a lot of that in response to this particular column; for example, as one guy wrote, "Porn focuses on body parts, not on sex. This is how bestiality develops." Yes, we see that all the time: One week, a guy's surfing the net for busty blondes; the next, he's got the hots for the neighbor's Labradoodle.