I'm not trying to defend DEF CON's overall actions here, but in this case it looks like the physical interaction itself was essentially consensual? The goons as

I'm not trying to defend DEF CON's overall actions here, but in this case it looks like the physical interaction itself was essentially consensual? The goons asked Dmitry to leave, his response indicated that he wasn't going to leave voluntarily on his own but also that he would cooperate with a minimal physical display that demonstrated the non-voluntary dynamic. I suspect that if he had physically resisted or even just gone limp, they would have escalated to actual security guards, who then may have laid actual criminal trespassing charges (if for nothing else than to cover themselves).