Got to say that I agree, it was moronic behaviour, regardless of skin colour. They were obviously bully-boy tactics to mess around with stopping people getting on the train, one bright spark (!?) started a ridiculous chant (as happens to people after too much booze or substances) then it all becomes a "racist" incident.
It's ridiculous. They were being prats, full stop, it doesn't matter who they were being prats to, they were being prats.