"Mzungu!” I hear the children shout when I walk past their playground. Instinctively I turn and wave, already well attuned to my Rwandan name of "white person” I hear shouted affectionately almost every second day."Does this offend you?” my colleagues ask when we discuss my informal naming. The answer is no. Not one bit. For the children, my white skin is a novelty. Their enthusiastic calls are signs of naïve excitement. It makes me happy to see them smiling and waving like a long-lost friend.My white skin is no secret. Yes, in Africa this can be a rare thing. But as a South African, I am an African too. Just a slightly paler one.Someone describing me as white would be the same as someone saying I have green eyes and brown hair. These are mere observable, objective facts.What does offend me however, is when flippant racial comments made by other white people, indirectly affect how I will be perceived.Over the weekend, a lady named Justine Sacco tweeted 12 words before boarding a flight from London to South Africa. She typed: "Going to Africa. Hope I don’t get AIDS. Just kidding. I’m white!”Whilst she was flying, the world on the ground erupted with indignation and her tweet went viral within a few hours. The hashtag #HasJustineLandedYet was trending within the hour.Needless to say, the press waiting for her at the airport were not hoping for autographs and her PR job she had before take-off was no longer hers upon landing.Undeniably, Sacco’s inability to respond to the waves of anger, criticism and disgust that were flung at her whilst she was far from any decent wifi, reeks of an imbalanced argument.Any fair debate relies on the notion that both parties will be allowed the chance to respond, even if that response is completely insipid.Unfortunately for Sacco, her response came too late."Words cannot express how sorry I am, and how necessary it is for me to apologise to the people of South Africa, who I have offended due to a needless and careless tweet,” she wrote to South African press.That she used words such as "ashamed” and "insensitive” and, jobless and hated by most of the Twitter world, I am sure her adjectives were quite genuine.The speedy nature of social media means that every one of our 140 characters should be treated with the same care as a printed newspaper headline. Although, it has the ability to spread quicker and further than a headline, so perhaps it should be treated with even more sensitivity.Ultimately, Sacco’s flippant tweet will affect me and other mzungus around the world, especially those living in African countries. By default, there will be those that see me in the streets of Kigali and think I share Sacco’s  ‘‘sense of humour’’.This bothers me because I do not want to be affiliated to a stream of thought I feel is very far removed from my own.I suppose that one can only hope that when the dust settles, something can be learnt from all of this: Be careful what you tweet, don’t judge all mzungus by the colour of their skin, and remember Justine, Africa is a continent, not a country.The writer is a South African journalist travelling through East Africa and currently interning with The New Times.

Twitter: @KimHarrisberg