I have heard all of the arguments but if you're still active on twitter without a active presence on any other backup social networks, after the events of the last week, I mean, come on.
@hacks4pancakes @alyssam_infosec you can just say that you don't want to be on that site anymore and that if they want to continue interacting with you that they need to do so in an environment that is safer for you.
Give them the choice to do the right thing or lose access, and couch it as being a safety issue, and I think most folks will react well to that.
[I've lost a lot of contacts over the past few years who didn't feel like respecting my boundaries. It hurts, but I'm much better off having those boundaries respected...]