Funny how that argument only works with kiddie porn. I mean, you could argue that by buying Nikes you're encouraging and supporting child labor. You could argue that by buying a diamond you're encouraging and supporting slavery. You could argue that by buying pictures of Abu Ghraib the media "encourages and supports" the behaviour at Abu Ghraib.

But this supposed causal chain of responsibility between purchaser and producer is only enforced, indeed only even mentioned, when it comes to the bogeyman of child porn, which means it's nothing but an excuse.