Probably because of the "No Bitch Ass Ness" shirt he wore during his talk. https://twitter.com/MCHammer/status/259783902699339776
Partners at VC funds are employed (funded) by limited partners (LPs). LPs are typically institutional cash and tend to be conservative. A26Z's LPs and potential LPs would not be pleased if they saw a video of Ben giving a talk wearing his "No Bitch Ass Ness" t-shirt.