Yes, it's very distasteful, but it's not illegal as it doesn't demonise a section of society who have historically been (and are still) oppressed and mistreated for the way they were born
Can you really not see the difference between homophobic chanting and chanting about Northerners being dirty?
How many Northerners do you think don't attend football games because they're uncomfortable/upset with anti-Northern chants?