Let me make it clear up front that I know porn is a bad thing, for various reasons. About the only kind of defensible "porn" is produced by a husband and wife with and for each other only – and I'm sure there are people who can make a good argument as to why even that is wrong.
But it doesn't help our cause – well, my cause, which is NOT to outlaw porn but rather discourage people from supporting it – if we use bad arguments that are easily shot down.
One of those bad arguments is some variation of this:
"Porn creates unrealistic expectations or is unrealistic in its portrayal of women and sex."
When you stop to think about it, almost all media creates unrealistic expectations or erroneous or incomplete depictions of people or activities or situations. It is very difficult for any book, any magazine, any film, or any television show to give a complete, in-depth, and unbiased portrayal of anything. (Same goes for theatre.)
Even the Bible (which I consider at the other end of the spectrum from porn… by light years) doesn't give all the details of the events described, or all of the character traits of human beings from years past – just the ones relevant to the message. I believe the Bible teaches us all we need to know to have fellowship with God. But it doesn’t tell us what Jesus had for dinner most nights of His pre-crucifixion ministry.
Getting more mundane – what about romance novels? Jewelry ads? Soap operas? Crime dramas where the DNA is tested within minutes and matched instantaneously and problems are all solved in less than 60 minutes when you ffwd through the commercial breaks? What about sitcoms where husbands are constantly mocked and berated, yet still manage to be cheerful and romantic? The NBA doesn't give a realistic portrayal of most men. Most of us aren’t 6'7", trim with bulging muscles, and able to run for an hour and still make slam dunks while three other giants try to stop us. Even the news doesn't even give well-rounded portrayals of most people covered.
It is kind of silly to tell our sons (or daughters, for that matter) that they should not view porn because it is unrealistic, and then go out and buy them the latest superhero movie blockbuster for them on Blu-ray. I watch "The Lord of the Rings", and nobody from my church says, "You really shouldn't do that. It is unrealistic."
It isn't like porn gives realistic portrayals of men, either, but you rarely hear that complaint. There are women who look like that (especially with surgery). There are women who behave that way, too. So it isn't entirely unrealistic, even if uncommon. But it usually does glorify fornication and adultery and encourage illicit lusts – those are some valid reasons to avoid it.
Notice, I'm not addressing the "degrading" argument in this piece. That is another matter.
Let's not use bad arguments, unless we're trying to get a laugh. Porn is bad, but not because it is unrealistic.