Ah, the old "adding to lists as a form of harassment" trick, or, as I call it, the Picard maneuver.pic.twitter.com/UMi9TMRlAj
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
I also use lists in a non-malicious manner. But yeah, this behavior is common, and frustrating in that it circumvents Twitter's reporting system.
Well, think of it this way: If you are angering the passive aggressive wittle fuckbois then you are doing something right! :)
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.