I hear this all the time, but I don't buy it. NOW
doesn't have any major platform relating to issues that specifically men face. Even the National Partnership for Women & Families addresses men
only in broad strokes: their work and family section talks about greater leave, but its images only discuss maternal leave. Men just aren't their focus (and I understand why, and don't really even think that's a bad thing.) But at some point I feel like this argument that "men's rights organizations shouldn't exist, feminism is for equal rights" is like saying "why's there an NAACP?"
If men don't feel like current women's organizations address their needs specifically, then it makes sense for them to form their own organizations. I wish them good luck though, as you have the mindset expressed that "men's rights" is just code for "women haters unite."