Call them out when you see the kind of behaviour against minority groups of a variety with their intimidation tactics. Whether it is on the streets, in the workplace, in the supermarket, bar, or restaurant. Don't condone their behaviour by staying silent.
Like the guy at Leytonstone Tube Station when 3 people got stabbed by a hate-filled jihadist and called out You ain't no Muslim, Bro - everyone of us has to play a part in whatever way we can to call these people out and let them know they are not a part of our societies. That they represent nothing that our countries stand for.