Yes, it is disturbing. Very much so. SO much so that it was pulled from YouTube. (You can see it on Vimeo.) But, like the Wikileaks video, it's the kind of disturbing that is worthwhile. The kind that is necessary. If you are an adult and willing to deal with shocking content, I'd recommend you see it. You aren't going to like it, but you'll have appreciated seeing it.
Pretty much anybody with a clue (and, who, especially, knows anything about the UK's cultural idiosyncrasies of prejudice) will know instantly what sort of allegory is going on here. It's about showing how minor prejudices can become major ones, and about how the sort of prejudices that you cavalierly ignore or explain away—because you don't identify with the victims—can be brought to vivid life when they're people that you can identify with.
(If nothing else, I'm never going to see certain episodes of South Park the same way again.)