Prima facie what happened to Mark Osborn is reprehensible. However it is only one side of the story. A former member of Workers Liberty has said on Twitter that Osborn is a racist. Jeffries I have encountered (on the web) in his previous incarnation as dogmatic (2007) crisis-denier in chief for the 20 or so members of the "Permanent Revolution" breakaway from workers' power. It does sound from Osborn's account as if they were involved in quite a heated argument, following a meeting in which Osborn (by his own account), in his one-minute contribution, managed to call other people on the left anti-semites (presumably without any corroboration since he only had one minute). It does not sound like the wisest course of action but I agree there is no excuse for physical violence.