I doubt this removal is anything sinister. Attacks on Tor have been a relatively common theme at many large security conferences. For example, there was a presentation at IEEES&P 2013 on de-anonymizing Tor hidden services (http://www.ieee-security.org/TC/SP2013/papers/4977a080.pdf). The Tor people are typically pretty open to this stuff. It was most likely removed due to something mundane, like the presenters having issues getting through their organization's bureaucracy.