I agree with this, and with the comments basically saying that Barnes can't be blamed for passing on what he heard. He passed on something from someone at the club (99% certain it wasn't Donald, but still), and people would have gone mad if he didn't. As mentioned getting confirmation would be difficult due to the small number of people involved and the likelihood of NDAs etc.
The only thing I would say is that, having passed that on and in a fairly specific way in terms of timescales and the likes (which had presumably been given to him by someone with knowledge of how long things take and what stage they were at), it's a bit of a shame that he doesn't seem to have been pushing for a further update as the season gets closer. If I'd been told something and had put it out there, pretty much at the behest of the club, and was then constantly getting questioned about it, I'd be back onto the source asking for some sort of update. Maybe he's doing that in the background like, but for all I think a lot of the criticism is way over the top, I don't think it's asking too much to want him to try and follow up on it.