- do not understand what pleasure is, and what it looks like in reality, OR
- make themselves believe that the fake images are in fact real; OR
- obviously don't care about other people's pleasure but their own when it comes to sex...
In any case, if that's how you think, there's something seriously wrong with you. Either because you've got a fucked up notion of what constitutes someone who genuinely willing to participate in sexual activity, or because you don't care about other people's enthusiasm, willingness or consent.
Which, of course, makes you a sicko and a wannabe rapist.
Most people accept the argument that, in child pornography, the minor participants are not *exactly* enjoying themselves, and that people who get off at this are would-be criminals who are sick enough to make themselves believe that this is for real.
Why don't people then also accept that the same is true with respect to "adult" pornography, and that the people who use it and get off on it are equally sick?