Does their non-visit make the conclusion less valid?

OK, they didn't come here.  It's not hard to review the materials, background, statements of displaced public housing residents, etc.  Look at the conclusion from the report:

Kothari and McDougall's statement made the case that public housing plans in New Orleans amount to a violation of international human rights law. They say "the inability of former residents of public housing to return to the homes they occupied prior to Hurricane Katrina would in practice amount to an eviction for those who returned or wish to return." In telephone interviews, they later called for a one-for-one replacement of any public housing units that are demolished.

Honestly, does one need to sit on the stoop of a project apartment and have lunch to be able to draw that conclusion? (Even if the food is better on the stoop.)

Of course, the UN doesn't advertise in Da Paper, so this article is not surprising.