Using TOR for torrenting is considered to be rude, since you're taking away bandwidth from people who are using it to, y'know, access news outside of China and stuff.
This is true, especially when you are sending Data across the TOR network, but you can set up most clients to only resolve the hostnames using TOR, leaving the actual Peer to Peer transferring to the main network, depending on the type of blocking the ISP is utilizing, you may not need to use TOR for full Data transfer.
OH, and note that TOR has it's own hidden service torrent tracker now... so... that taboo is slowly dissolving as the network gets more exposure to higher and higher bandwidth relay nodes.
Plus... If run as an exit node, you can offset the detriment by providing your bandwidth to those who need it... an ethical exchange of data transfer bandwidth... however, you might want to look into getting your
gonads encased in steel, as TOR is also used as a cover for illegal activities... The alternative way to help is to run as a Relay node... it greatly increases the network's overhead without the risk of a Police action.