You seem very passionate about defending alleged harassers. I just wonder what fuels that. Perhaps you think these events are not that bad, or some degree of inappropriate behaviour is ok?
Sometimes people who are keen to defend harassers might do so because they exhibit similar behaviours themselves or hold similar beliefs and want to defend themselves.
Here is an example from this very story: Caldbeck tweeted in support of Uber: "Also mob mentality w @Uber right now. Guilty before proven innocent on everything".
I genuinely think it's worth self-examining one's motivations if someone's first instinct is to defend the man in such a case. I say this without trying to accuse anyone, sexism is subtle and affects everyone, and it's through self examination that we can grow and improve.
Ad hominem being acceptable on a few pet issues is a value system I've noticed that many people, including you, have. I would ask why. I've had this turned on me, too, hence why I'm not surprised; I'm reminded of defense lawyers who receive death threats and actual violence, as well.
Why do you assume it was his (or her?) first instinct? This HN thread has already well-established that Caldbeck's behavior is repugnant. Do we need every single poster to +1, or can people propose questions for discussion without being accused of being part of the problem?