Assuming all of that material is in fact illegal to distribute in that jurisdiction (I have no idea about their copyright laws) that still says nothing about what percentage of the overall torrents are illegal material, just that the illegal torrents are far more popular.
On the recent page at this moment (http://thepiratebay.org/recent) , 90% of the torrents are of copyrighted content not being distributed by the rights holders. Two of the legal ones, I believe, are the porn picture sets. They are used to promote pay porn content and I will give the uploader the benefit of the doubt here. The other one is someone's collection of recipe for Indian food. I'm similarly assuming that his collection of recipes is not copyrighted, but 15.9MB of recipes is a lot of personal recipes.
Look: I am not in favor of the current system of IP. I think it is ridiculous to artificially add some constraint of scarcity when the marginal cost of duplication has fallen to zero. But we're reasonable here, we're not in court. We don't need to defend TPB using legalistic arguments. We can just be happy that a group of high powered lawyers turned out to be completely incompetent.
This doesn't matter though. If the majority/all of the most popular torrents on that site are illegal then the most popular use of the site is for illegal torrents. If most of their users go there to download illegal torrents, then that is the actual function of the site -- to share illegal downloads. It doesn't matter if that was originally intended to be so or not.
Ah, but you're not countering my argument. I'm not counting bandwidth -- I'm counting people. If most people on the Internet spent their time downloading files illegally then sure, that would be the main usage of the Internet.