It's not that they researched what to say...that just sounds silly. It's just, as much as how you feel they're doing something ethically wrong, they feel they're doing something ethically right (or righting a wrong).
They put up videos on torrent sites (and teach on Youtube) because they feel that the amount you pay isn't equal with the content you get. When you're spending $25 or more per trick, they feel that
that is ethically wrong--that we should be paying far less. So, one person gets the video, and either uploads the actual video or makes a Youtube video revealing it; essentially, the person thinks he (or she) is Robin Hood--stealing from the rich, and giving to the poor. He sees what he's doing as noble and the right thing, righting an ethical wrong.
What's my point? Yelling at them or arguing with them, etc, isn't going to work. In the end, your time was wasted, and (despite all the praise here),
you end up looking silly for taking such a silly path to try to stop them. If you want to make a difference, you have to change their belief system, and that process does
not include arguing with them--in fact, arguing just deepens their current beliefs, so really you're just making matters worse. What's a better solution? I'm not sure. All I know is that by arguing with them, the situation isn't going to change for the better.
Think about it--if he started calling you stupid for paying for magic when you can get it for free, would you change your mind so easily? Probably not, as it seems you're pretty deep seeded in your beliefs. Well, guess what? So are they.
Moral of the story? If you want to make a difference, try focusing on the roots of the problem, not the leaves.