What's wrong with being a member of the Federalist Society?

One thing that I really don't get is why so many people get in a huff about a lawyer's membership in the Federalist Society.

From it's Our Background page:

Founded in 1982, the Federalist Society for Law and Public Policy Studies is ... dedicated to reforming the current legal order. We are committed to the principles that the state exists to preserve freedom, that the separation of governmental powers is central to our Constitution, and that it is emphatically the province and duty of the judiciary to say what the law is, not what it should be. The Society seeks to promote awareness of these principles and to further their application through its activities.

Sounds like good principles to me.