Personal Experience: Several months ago "my" Witness shows up at the door to drop by copies of The Watchtower and Awake. This time he's accompanied by one sister. I had planned to carefully broach the UN topic by relating personal history.
I told the Witnesses that back in the mid-1990s I had brief contact with individuals temporarily serving in low-level UN positions/personnel slots. In those days all sorts of groups maintained an association with the UN, to include the Watchtower Society registered as an NGO with the UN Department of Public Information.
I expected denial and perhaps anger. They presented neither, although I may have noticed some suppressed surprise.
The Witnesses accepted my story and even seemed to believe the Organization was still registered as an NGO with the UN. According to them, the association is justified for legal defense. Being a UN-associated NGO allows them to defend themselves in human rights cases such as those involving religious freedom in Russia and elsewhere, securing them the right to appeal to the World Court in the Hague. Biblically, they cited Romans 13, being in submission to worldly governments is legitimate for true Christians.
They stressed they did not consider the individuals I had known who worked for the UN as evil; it's the UN organization as a political entity (?) they consider a Satanic agent of Evil (?).
Further, they offered the analogy of the incorporation of local congregations for legal status and defense – people cannot sue the elders, they have to take on the congregation as a legal whole. I asked about the status of the individual Witness liaisons with the UN; they evaded answering and moved the conversation toward registering for the military draft. Witnesses can register but will refuse to serve in military forces. Alternative service is OK, and they gave me examples of brothers who, at the time of the Vietnam war, chose to go to prison and another who accepted alternative service.
Impression: These folks had no sure knowledge of these issues. I strongly suspect they were impelled to tell me anything semi-logical to clear the Organization of hypocrisy.