This is actually a great example of how modern day propaganda works. One tactic to discredit someone is to combine two true statements by them that look similar to create a false statement. Case in point:

Claim 1: Trump says he was against the war before it started. In the Cavuto interview he's questioning the war, and he says he used to argue with Sean Hannity about it. Sean Hannity backed this up. There's no reason to doubt this.

Claim 2: Trump says he's different from his opponents because he came out strongly against the war before anyone else did. That's a fact and there's plenty of evidence.

Then comes the spin. The media will mix the two statements together to say Trump said he came out strongly against the war before it started. They'll use this to call him a liar. Try to find me one example of him saying he came out strongly against the war before it started. You can't, because he never did.

This is why people don't trust the media.