One thing I do find odd about the article is that she said the guy called her a slave... That part doesn't sit well with me. Is she sure it was a Brit that said it? Look I'm not even going to attempt to deny that there isn't racism in the U.K. There is, I know it, I live in Barnsley which is pretty notorious for its racism. Which means I hang about with racists quite a lot. Not once have I heard them use a word like "slave".
Its not something a Brit would say. We don't really have that kind of culture if you understand. Slavery to black people isn't seen as a big part of our history (we did do it, no denying that but its not something that most racists here would think of). That sounds more of an American racial slur given the meaning of it and how deep it is in Americas history.
That and well... They'd be no way of knowing who this girl is or her country of origin. So they'd be little context in the racists mind to use that slur. Look I'm about to say some nasty words here so if your offended look away. A racial slur from a Brit would be more on the lines of "Coon, Gollywog, Paki, ****** (not quite as common though) foreigner, ginner and so on" Slave really isn't one I can see being used.
I'm not denying that he said something, perhaps he called a "silly black ****" that's something I'd imagine coming from a Brit.
As far as the crowd not saying anything. Us Brits are almost famous for being reserved. Even if we didn't agree with the prick or thought it was horrid, we'd keep it to our selves or probably discuss it to the person next to us quietly. We're not the type to start screaming out because it would cause a fuss.
That being said, even if this prick did start screaming slave and was a Brit. Despite all I've said, shes still in the wrong for blaming an entire country on the actions of one silly racist. Though honestly, I just imagine her getting told off for pushing in (which is a big deal over here... take it seriously, shit'll get you killed) and going over board over it.