I don't believe that the difference is serious vs non-serious events. It's pretty clear that no company or group would dare to create a light hearted hackathon featuring sexual content, if it hadn't been proposed first by a progressive cause (in this case mocking startup culture for being a White cishet male bubble). And Microsoft apologized for that song[0]. Note that this event is sponsored by real tech companies.
Here is the content I thought would be considered offensive it it didn't come from a progressive source (repeated from [1]):
Here are some examples from the previous New York hackathon [2]:
Sexual content:
Golden Bitcoin Pasties, Focus Tools, Collaborative Fuck Bike, E.T. Strapon, Sado-Masochistic Macrame Planter, Tinder For Babies, "ok glass, vomit"
Making fun of mental health/development issues:
Stupid Font
Body shaming and objectification:
Intellectual Babes Calendar
And here are some prize categories in the current hackathon that are similarly offensive:
Peter Thiel, Scatological APIs, Targetting The "Hikikomori" Space
[0] http://www.zdnet.com/article/microsoft-apologizes-for-cringe...
[1] https://news.ycombinator.com/item?id=9521510
[2] http://www.stupidhackathon.com/