The "nothing to worry about if you have nothing to hide" argument has been debunked countless times and made the front page of HN in the last week at least twice. Privacy is a building block foundation for freedom. You can't have freedom without privacy.
Your utorrent encryption is merely useful to thwart some forms of bandwidth throttling, it is not hiding you or your sharing/downloading.
NSA could do such MiTM attacks, it's been a known possibility for years. but why would they rely on this kind of attacks as they probably have a copy of the private key of the party your communicating with (or something along these lines as was shown with lotus notes).
Also they already have other ways to seize and freeze assets, so you shouldn't have to worry about this specific abuse. There's more than enough to worry about the rest.
Turning on encryption is a way to work around bandwidth throttling and deep packet inspection, not a method to protect your identity or activity.