What are they going to gain?
Really? They've built an image of being family friendly - that's been their trade since the get go. You can say it's a bad one, but Nintendo has been fairly consistent.
NoA probably doesn't want their game being associated with the various FGC stigmas and:
http://www.youtube.com/watch?v=pD_imYhNoQ4
it's outside of their image and ruins their business.
That's probably their thinking.
I'd like to hear the retort here.