See... that's about the argument I'd been making and I had just about given up. I also think that nuance is important.
Does not change the fact that the whisper didn't push him to accept the WK mantle, only how to deal with it.
These two statements don't contradict one another. And I agree with both of them, myself. I just think that, while the Whisperer's ultimate goal was that Harry should kill himself-- and it used the necessity of him becoming the Winter Knight to get him to that point-- the only thing that the Whisper changed directly was whether or not Harry would talk to Uriel.
At first I was thinking along the lines of, Harry was going to be the Winter Knight regardless of whether or not the Whisperer said anything to him, and probably regardless of whether or not he talked to Uriel. That is, if Harry hadn't been influenced by either one, he still would have become the WK. But then I realized that that third option was never on the table; we got to see how Harry would behave without the Whisperer's seven words, and Harry chose to call Uriel. Which meant that the only paths he was ever likely to have taken were the one in which he talked to Uriel and the one in which he heard the Whisperer. In my opinion, those are the two main points of difference, because those were the two points at which he made his decisions.
Basically, I think Harry was already on the road to killing himself, but, because of his choices, he was going to be saved by Uriel giving him hope. The Whisperer closed off the branch of Harry's future which would have given Harry hope, so Harry went with his prior inclination, which was to assume the worst about himself becoming the Winter Knight, which in turn led to his decision to kill himself.
Though, you know, thinking about it here, I'm having a hard time remembering why this minute distinction between theories matters at all. Most of us seem to be thinking pretty much the same thing, we just seem to have different ideas about which point in the chain of events was most important.