Devil's advocate.
This petition will not have him fired; obviously this is just the actions of a disorganised individual, and cannot be blamed on the movement as a whole, as you just dishonestly did. Sometimes people respond to something that, like this, legitimately infuriates them in a non-strategic way. If you're concerned about that, join the movement and help it organise.
That said, Lemon was clearly being an idiot, or perhaps trying to cover up racist assault. This media rage lasts a few days. If you can sell an event as "beyond politics" or "needing more investigating" for a week, everyone forgets and he systematically does it again, the student is kicked out or otherwise bullied and nothing changes. You have to lock in change immediately, that week. Investigations have to start straight away; legislative change has to start immediately. Anyone who opposes that supports the crime.
Finally, it is useful for this sort of thing to happen for the simple reason that people should, through fear perhaps, be required to think before they speak on these sorts of issues on live TV.