There is no question that fgm is indeed medically harmful, a human-rights violation, and a twisted, relatively modern expression of patriarchal control, however much the senior women in a community may participate in enforcing the continuance of the practice.However, you do not have to be a "relativist" to refuse, at the same time, to be a smug, superior, self-righteous, unreflective Western imperialist, aka a pompous blowhard.
There are ways and ways of approaching fgm, especially if you find yourself suddenly talking to a young woman immigrant to this country who has had the procedure imposed on her in youth. Those women don't need protest signs shoved in their faces by arrogant Western men, and they don't need to listen to insensitive, superior lectures from them either.
There are organizations in Canada that are in no way "relativist," staffed by women from some of the cultures where fgm has been a problem, who are both fighting the practice but, at the same time, able to work in genuinely humane and positive ways with women from those cultures.
Further, I would be shocked to hear that any UN agency or Amnesty International accepted the stark binaries set up in that article. People who work for the UN in countries that have been plagued by fgm tend not to be spending their time inventing straw-man arguments, and tend to be as sensitive as they are capable in their interventions.