The WTS was never members of the UN. (Likewise Witnesses weren't either. The WTS and the JW religion are different legal institutions). Only national governments can be members of the UN. All other organizations can become associated with the UN as NGOs. The WTS sought for and was granted NGO status. The UN website has an entire section on NGOs and their role. To become an NGO, that organization has to agree to the principles of the UN and help promote the UN. That's where the hypocrisy comes in.
Just to be a little more picky. The Watchtower has and always will be a non govenmental organization (ie. a not for profit corporation). To become an "associated" NGO with the UN's Department of Public Information (DPI) the UN has to agree to the principles in the UN charter and to promote (dissiminate information on) the UN and must re-new its associated status annually. NGOs can also receive "consultative" status with the UN's ECOSOC but the WTS never did that.
The UN literature shows this to be a "partnership". The 1991 Watchtower article - Their refuge - a lie! clearly shows this to be a no no.
BTW - well done getting that information to the "sister". That will get some cd going.
hawk