It is astonishing that the police were largely missing in action, and that arrests were pitifully few, a full 24 hours after the eruption of large-scale violence that has all but shut down our capital city.Dozens of buses and trucks have been torched by marauding mobs, shops have been looted, foreigners targeted, highways blocked and government departments forced to close early as the protesters - mainly ANC supporters, despite attempts by Luthuli House to disown them - ran amok.The rioters' excuse: dissatisfaction with the ruling party's choice of a mayoral candidate for Tshwane.Imagine what would happen if the ANC, which is facing strong challenges in the metro from the DA and the EFF - lost the city to the opposition in the election on August 3.The excesses in the Pretoria CBD, Mamelodi, Atteridgeville, Hammanskraal, Mabopane, Ga-Rankuwa and elsewhere in Tshwane are a stain on our democracy.They contribute to perceptions that South Africa is fast becoming an unstable, dangerous country - at precisely the time when we are frantically trying to attract investment to kick-start growth and create desperately needed jobs.For this reason, the thugs who loot and burn, and who terrorise innocent people, must be arrested, rapidly prosecuted and given lengthy jail terms.We appreciate that policing under these circumstances is difficult and dangerous, and that the police are under-resourced and on the back foot after the Marikana massacre, but examples need to be made of these criminals.For far too long, thugs masquerading as citizens with genuine grievances have been given a free pass after burning schools, petrol-bombing lecture halls and destroying state infrastructure.The ANC - deeply divided, and plagued by factionalism and corruption - also needs to take a long, hard look at its internal democratic processes...