I'd say Play4Fun hit the nail on the head.
Most of the outwardly anti-N developers started out or really hit their stride as PC or PC style developers. The other consoles cater very well to PC ports there for opening the doors for these companies to leave the relative obscurity of PC software developers and into the glitz and glamor of the major console developers. Along comes Wii, which proceeds to mop the floor in sales, but has nothing these former pc developers can use to get in on the party.
On a business level, it makes total sense for these companies to not support Nintendo, because it is not as easy as the other consoles, and carries much more risk.
As to why some developers choose to publicly bash any console, that's just douchbaggery and totally unnecessary.
LISTEN TO THE FIRST WORLD PODCAST REAL GAMERS, REAL AWESOME
