I believe they know they are deceiving the members but delusionally think that they're deceiving the members for their own benefit. It's a case of having the mindset that the end justifies the means.
Did you see the JW broadcast where Samuel Herd was addressing the issue of JWs being brainwashed? He did not deny it. Instead his argument consisted of saying that what others call brainwashing is seen by them as wholesome teaching and mental readjusting to clean the mind of the corruptions of this world. That's not a quote, mind you, just my paraphrasing of what he was saying. So he essentially justified brainwashing by putting a positive spin on it!
I think they similarly justify and rationalize their deceptive responses about issues like the UN fiasco and child sex abuse. They probably tell themselves that it is in the best interest of the brotherhood that they not know the whole truth about such matters so as not to discourage and stumble them. They probably rationalize that the negative publicity that would come to the organization if all allegations of child abuse are promptly reported to the police, is of greater importance than the welfare of the individual child abuse victims, so they feel justified in sacrificing child abuse victims and covering up the issue in the name of protecting the image of the organization so that outsiders wouldn't see the organization in a bad light and be stumbled away from accepting the truth.
I would say it boils down to doing evil in the name of God. But its actually doing evil because of organizational pride. Organizational pride is at the root of the child abuse mess they're now mired in.