I guess they are different than the average viewer in the US. An example given were a black man wanting to cross in the middle of a KKK rally. The average US person would want to know if this guy is a complete idiot.
1) KKK have a right to rally in the United States. They would not be able to say white supremacist slogans in the UK.
2) if the KKK rally in the US started threatening specific black people it would be fighting words and they would lose their free speech protection and they would absolutely get arrested.
3) If it was a legal march where the cops politely requested a black person to use a different route, maybe. But if the black person still wanted to walk on a public street and was getting threatened by the KKK, obviously the people that should get threatened with arrest are the KKK members, not the black person exercising his rights.
In other words: cops politely ask = ok. Person can choose whether or not to listen
Cops order to move under threat of arrest= unlawful order violating the citizen's rights.
I don't know what legal protections people have in England, but in the US the cops in this instance would be personally liable if they arrested him unlawfully and would not get qualified immunity. And based on the fact that this is clearly policy from the top, the city would be liable as well, especially when the cops would inevitably implicate their superiors when they tried to defend themselves.