Both of the witnesses' testimonies seem to be subjective: "It was getting creepy, but Justine didn't move, or slap him. She was laughing..."[1]; "The executive's posture and actions aggressive; "no" was not a possibility."[2]
Their stories also don't corroborate: "Fast forward to (from what I remember), around 1am. "[1]; "It was slightly before midnight..."[2]
I think it is good that there are witnesses but it is not as simple as saying that because there are, Justine's version of events is correct. We don't know exactly what they saw and heard, how much of their versions are based on actual events or the aftermath or their relationships with the involved. That is why it is still important to maintain innocence of the accused until proven guilty.
"Here is something I find curious: you are one of many commenters here...bringing up the hypothetical, irrelevant possibility that such an accusation could be made falsely"
It certainly isn't irrelevant to the accused. His reputation and in fact his entire life is at stake. A few blog posts do not constitute proof.
[1] - http://blog.matt-darby.com/essays/i-am-the-other-developer
[2] - http://theotherzach.com/writes/2013/10/9/events