To be scrupulously fair because that's how I try to roll, it doesn't necessarily have to be actively evil, just the law of unintended consequence. The way LJ (and DW, since we're a code fork of LJ) is programmed, the best way to keep someone from posting or commenting while logged in until they agree to a new version of the ToS just so happens to also fire when you're using the XML-RPC protocol to download journal contents, and DW's importer uses the XML-RPC protocol. That "you can't do anything until you agree to the new ToS version" was actually added ages ago. (I want to say ...2005? 2006? Something like that. While I was still working for LJ and it was still owned by Six Apart, at least.) So, it's possible the current team went to go build a ToS check, realized there was support for doing one already in the code, and enabled it, without specifically realizing/actively deciding that it would also block people from accessing their data through the XML-RPC protocol.

Mind you, I don't know for sure one way or the other! I just like to point out when the fail is possibly accidental instead of having to automatically be malicious. :)