Lets have a little think about this situation, shall we?

I'm sure we can all come up with a hundred and one examples of Jhonen Vasquez giving contradictory explanations for certain things about the show. Thats the way he is and, lets be honest, that makes things interesting for us as fans. But lets assess the Bloody GIR situation without the death threats...

The official reason for Invader Zim being cancelled was low ratings. That was the reason officially released by Nickelodeon. Now, we all have our conspiracy theories. Of course, it is entirely possible that Nickelodeon cancelled the show because of the Bloody GIR image and then tried to cover it up by blaming ratings. That wouldn't surprise any of us. BUT lets keep in mind that this is a fan-concocted theory. No official source has ever said that the reason that the show was cancelled was due to the Bloody GIR image. In addition, the reality is that network representatives go over the shows they air with a fine-toothed comb. That is, they watch the show before it airs to make sure that there is nothing against the rules in the show. IF they had found the Bloody GIR images, they would probably have told the show's producers to remove the images. IF they HADN'T found the images before the show aired, the producers may have gotten in trouble after the show aired.
BUT, the reality of this situation is that if Invader Zim had been rating phenomenally highly, the network would not have cancelled it, even if it did breach the rules, because the network wants to make money off of it. That is why Nickelodeon replays Invader Zim every now and then: to cash in on its cult status. If Nickeldeon had really cancelled the show because they thought it would offend people or because it breached the rules, they probably would not continue to air it.
The reality is the ratings and the financial success of a show mean a HELL of a lot more to a network than whether or not a Bloody GIR appears on screen.

Also, hating "people who support bloody GIR" is not exactly the nicest thing anyone has ever said here. I personally like the image of bloody GIR because I am pro-freedom of expression. And I think that images like that in a kids show show a great deal of respect for the intelligence of children. Children like to feel a little scared and a little uncomfortable sometimes, to test the boundaries. It is naive and insulting to all our intelligences, whether we are kids or adultsm to assume that an image like the Bloody GIR would be damaging to us. So I would rather not have the death threats just because I can appreciate what the Bloody GIR represents TO ME. Supporting the Bloody GIR does not support the cancelling of the show, it supports the idea that Invader Zim is a cartoon that pushed the boundaries, challenged me and fought for the right to express itself in a unique way.

Personally, I would rather think that the show got cancelled for being edgey rather than because people didn't watch it at the time. To me, that is proof that Invader Zim is a cartoon that respected kids enough to say "We know you kids are smart enough to deal with these images, so we are gonna show them to ya". THAT is why I love the show and THAT is why the show has the cult status it now holds.