Gay Heroes

The supporting character of Zach on the TV show Heroes is gay.

Everyone knows that... including show creator Tim Kring and the show's writers (the show's official site admitting the character's sexuality in a transcript).

Then all of a sudden, Zach "is not gay for sure" according to an NBC spokesperson.
(The mention on the site transcript has been edited out.)

So... Why???
What (social?) pressure forced NBC to erase any homosexual from their hit show??