For most, what we see in real life is mundane. But those who wish to fan the flames of anti-immigrant feeling share a different image online, says Guardian columnist John Harris

For most, what we see in real life is mundane. But those who wish to fan the flames of anti-immigrant feeling share a different image online, says Guardian columnist John Harris

The Belfast riots are only the latest anti-migrant protest fuelled by social media – and the violence could escalate