The thing is, as bad as the early call was, it is not certain that Bush lost a net ammount of votes from the early call.
What you have is circumstantial evidence and a few anecdotes from people who felt it was pointless to bother to vote after the early call. Note that the key word is "evidence". It's knida like Starr's replacement for Whitewter who said he didn't have enough evidence on Hillary that would lead to a conviction. He didn't, however, say he didn't think she was guilty.
Indeed, it isn't difficult to imagine that it had an effect, and no one is denying that it probably did. But is there real evidence that it mattered? No. Simply an educated guess.
Besides, if "anecdotal evidence" means so much as ten people saying that they did not vote because of it (and I saw at least ten such interviews at the time), then that is sufficient. The "probablity" remains that there were far more than ten. Far more.