Whether the source is open doesn't matter, and in fact I think that's part of a distraction; it's orthogonal to the issue of whether the software respects the user's freedom or is a way for a third-party to control the user (turning it into a "used"). Both closed and open source user-hostile software exists, and the same goes for software that isn't user-hostile.

Also, I suspect many of those who are anti-WEI are also either not Windows users, or Windows users who are grudgingly doing so and have also killed off the spyware and customised the environment to their own liking, which can still be done even without requiring source code.