I'm not so sure about public shaming. I'm in absolutely no way defending racism or homophobic behaviour, but trial by social media is not the right way to proceed. Identify the individuals, put them through the courts, hit them hard with lifetime bans etc. and then put their names in the press - as we would do with any other crime.
IF, and I know it appears unlikely, but there is the chance that the incident at the Manchester derby is dropped before getting to court. But that guy would have likely lost his job by then and will be seen as guilty by the nation. That makes me uncomfortable.