I was a long way away from the Twin Towers in September 2001 and when you're young you're less inclined to think yourself into the experiences of other people, so after a while I became a little irritated with the American post-9/11 trope of the heroic fireman.

It was everywhere. There were murals and posters and shout-outs in TV shows. There were famous comic book images of Batman walking tattered from the dust column carrying the broken body of a fireman; a humbled Superman bowing his head and murmuring, "You're the real hero" before a fireman like the Stakhanovite worker in a Soviet propaganda poster. Yeah, yeah, I thought. Firemen are brave, I get it. Enough with the firemen already, they're just doing their jobs.

But that's easy to say when the job you do doesn't involve walking towards the thing everyone else is fleeing. On Wednesday in Cape Town while the rest of us were bellyaching about a heat that drove through the city like a nuclear blast, the kind of bone-bleaching solar wind that turns the air yellow and makes you laugh in disbelief because you think someone must be playing an elaborate practical joke, the firefighters of the peninsula were donning boots and heavy tunics and two layers of gloves and bandannas and balaclavas under their helmets. While we fussed and twittered, they put themselves between us and a roaring, moving wall of black-and-orange flame. Some of them worked 24 and 36 and 48 hours without stopping, their eyes burning and their throats thick with ash. Many fought for days to protect a part of the world in which they have no personal, material interest.

The first photos of the firefighters were stunning and eye-prickling. There they were: black firefighters and white firefighters and coloured firefighters, men and women, the poorly paid and the volunteers, smiling, tired, their joints popping and their heads swimming, keeping us safe. In a South Africa so riven along lines of class and race and urban geography there was something additionally emotional about those images, as though this were a scene from a Rainbow Nation fairy tale, composed when people still believed the Rainbow Nation was imminent: citizens, citizen-heroes, fighting side by side against a common foe, protecting a corner of South Africa just because it is South Africa and they are South Africans.

And there is some truth in that, but of course like all Rainbow Nation merchandise it conceals more than it shows. As Osiame Molefe pointed out this week, we didn't see these scenes and images during the shack fires in December, not because they weren't happening but because those fires didn't attract this degree of media attention and middle-class chatter. There are good, innocent reasons for that - those were numerous small fires, this was one night-brightening photogenic conflagration - but the fact is that what was truly unusual about this fire wasn't as much its size as the fact that the homes it threatened didn't for the most part belong to the poor.

You can, if you try, understand the anger in some of the responses to the outpouring of anguish this week. Poor people, shack dwellers, black South African lives are easily ignorable; they aren't luxury hotels or wine farms or landmarks. This is something that Mohamed Atta and Abdulaziz al-Omari and their fellow hijackers understood in 2001: if you want the powerful to notice you, destroy something they think they own. Tear down a tower; burn down the mountain.

We - people like me - feel ownership of the mountain. We feel a kind of ownership of Groot Constantia and the Tokai forest and the tortoises and fynbos. We even feel an ownership of luxury lodges that we ourselves couldn't necessarily afford to stay in, and that's a little weird, but it's not reprehensible. But we don't feel an ownership of the shacks or any kinship with the lives inside them. They're invisible, except when we're complaining that we can see them. The December shack fires destroyed some 700 homes and all the accumulated possessions and history of the 700 families that lived in them. Nearly two dozen people died brutally, in terror and with almost no media attention. The same heroes of this week worked equally heroically then, but the rest of us didn't care as much.

People like me felt horror this week because we felt helpless. A powerful force was loose and it seemed that it might not be stopped. We felt vulnerable, and we, of all the people in this city, with our cars and jobs and our household insurance and social networks, we are not vulnerable. This is what I am taking from this week: that firefighters are heroes, and that suffering is always worthless but at the very least it must teach us empathy.