Basically, this is based on the correlation that "hey, most of the stuff through a trackerless BitTorrent setup is pirated movies/tv, porn, and software, almost no pirated music" and "you can get DRM-free music easily, but not movies/tv, porn, and software" as implying "its because of DRM that people pirate stuff".
*sigh* Alright, let's look at the points you're making here:
Music is not just DRM-free, its also SMALL. BitTorrent's strength is moving big files, while pirated songs are very small in comparison, you can just email em to your friends.
Firstly, bittorrent's strength lies in distributing files efficiently when there is a high demand for them, regardless of size -- something which ordinary server-client scenarios aren't particularly good at. Even if what you're saying is directly and unambiguously true, it doesn't imply that therefore you shouldn't (or wouldn't) use it for small files. If you have a 100M connection, are you really just going to use it for movies^H^H^H^H^H^H Linux ISOs because everything else is "too small"?
A lot of porn online is DRM free, so why so much porn in BitTorrent?
This one's easy. Consider the possible sources of porn on the 'net: you can either get crappy quality on flash video sites, or decent quality downloadable files on paysites or P2P networks. A lot of people will feel reluctant to pay for porn, due in part to paranoia ("what if someone sees my credit card statement?", etc.) and in part to shame (in the same way you would feel reluctant to pay someone for sex). The only option that has both quality and anonymity is P2P.
I'm not saying you're right or wrong, just that your points aren't particularly well thought out.