The action was the public humiliation of somebody she disagreed with (as he made a sexual joke and she found it inappropriate) rather than handling the matter quietly. The consequential actions included: leaving a number of her own sexual jokes on twitter, making her seem hypocritical, bringing her employer into the fray as agreeing with her actions (probably without their permission), posting a blog post where she advocated speaking to people about things that make somebody uncomfortable, which is not what she did and not saying sorry when she found out that her public shaming had gotten somebody fired.

Later, it was discovered that she has a history of escalating potentially high-friction issues instead of trying to resolve them. This did not win her any sympathy.

How is it humiliation to repost a joke someone made in public? If he's humiliated didn't he do that to himself?

Publicly humiliating somebody is the use of mob rule to get justice instead of the existing structure we have all consented to (ie, the PyCon staff.) It also does not permit the person being humiliated to get in his or her side of the story. Thus, while the men might have done something stupid, inappropriate or even shameful, the public humiliation was done by her because she escalated by inviting mob rule instead of using the official channels.

While using mob rule may be a reasonable second alternative if the existing structure is corrupt and unresponsive as it can change who is in power, it is not an acceptable first solution.

I find a certain amount of delicious irony in the idea that somebody who tried to shame people using mob rule wound up burnt by a different mob. Shame there was so much collateral damage.