Bad post, starting with the title
I don't think that it's clear at all that Moore is commenting on Blackest Night, specifically, but a lot of commenters here seem to be skipping over that bit and accusing Moore of claiming to have invented zombies. Where are you getting that from?
OK, here's an idea: try reading the linked interview. Moore is actually saying that the degree to which his past work is dominating the TPB market (his numbers are possibly exaggerated, but whatever) is a bad thing. I can understand that some people may have a little bit of a problem processing that, because it's exactly counter to the pattern that most other superstar comics writers show, that of spending as much or more time self-promoting as they do writing. You can argue with the specifics of whether a particular character has been mined out--I think that Hercules, the Secret Six members, and especially Nova are getting written really well for the first time in their existence--but I think that he's absolutely right in that the comics market is shrinking for a reason.