Yeah, to me the liar label just cannot be applied to somebody who is predicting the future. The future hasn't happened yet so it's impossible to lie about it. It's certainly possible to be wrong in one's predictions but it is not possible to lie about an event that hasn't happened yet.
The left really likes the liar label. They called Bush a liar because no WMDs were found in Iraq. Bush was wrong about the existence of WMDs but how could he lie about something that was impossible to know given his position? Nobody in the west truly knew whether Iraq had WMDs and yet Bush was somehow a liar because his prediction turned out to be wrong. Sorry guys, Bush was wrong but he wasn't a liar.
I've even heard some on the left equate global warming skeptics to holocaust deniers. How can that be? The holocaust is a past event but global warming is only a potential future problem. There is no comparison.
Sorry to come down on you WBC but the whole liar language has been misused. I want to reserve the word for it's true meaning; somebody who says something that they KNOW is untrue.