I think Mr B is absolutely entitled to air his views, after all this is what a review site is all about.
Recently I had a girl cancel on me for the third time, and though I was miffed on the 3rd occasion that she had done it at least she got in touch with me first on each of those 3 occasions rather than me finding out otherwise. And gave a plausible reason on each occasion why she was cancelling. When we finally met up, the first thing she did was sit me down and was incredibly apologetic about the 3 cancellations, ending it by saying she was going to make the wait worthwhile!
Despite not knowing him, Little Katie should have been much more respectful to Mr B and sent him a private message giving him more details of exactly why she was cancelling on him yet again. If she had done that I don't think Mr B would have posted this, and may have been inclined to give her another chance. If I have interpreted the third cancellation correctly, Little Katie was relatively vague on the reason why she cancelled on him, all it does is give him the impression that she doesn't give a shit about him.