In the Uefa final in 2000, Arsenal and Gala fans fought each other, causing damage in the city. However, they probably would't set same rules for English. I support security, however, even if it is not racism, there's kind of a subtle way of saying, we don't want these type of people here, and generelizing everything. I've been to Manu vs. Gala, sitting with Manu fans to watch the game, nothing happened. Additionaly, for a European Gala fan it is almost impossible to buy away tickets to watch the game, because they are sold trough an agency in Turkey which sells them only with tickets and hotels etc. S pretty fucked up for a born Copenhagen local who is of Turkish origin, isn't it?
Edit: if you read the comments on the source page, one has a pretty good explanation. The article is not well researched it seems from there.