Well, I am a fan of Ben (I would've stopped buying Spider-man if he were revealed to be the "real" Peter, though.) and I can understand where Guggenheim is coming from ... as someone said above, all he's really saying is we'd never buy the false drama of the lead character being the murderer, but there is some doubt -- and judging by the responses above, there definitely is -- as to whether the writers would make Ben a murderer.
Honestly, I think we're being played either way and I don't really like it, but he's not 100% wrong.