Can't you see we've got brown skin? How dare you refuse to recognise our Get-Out-Of-Jail-Free card?
Some of their placards read "We are economic refugees" (!) and "Prosecute bankers not street-sellers". So these are basically Africans involved in authorised street-selling which the Catalan police have been trying to crack down on recently. They think it unfair that Whitey's laws should apply to them.