How you can add to graffiti to make it look less disgusting

Ever found some truly ugly and racist graffit on a bathroom wally? And you'll ask the restaurant manager to clean up the markings but the next week, nothing's been done. Why not take matters into your own artistic hands? I found this pic on reddit, where a user explained he liked to touch-up graffiti in a school bathroom to alter the image. What was once a swastika is now a smiling man running! While I haven't tried this yet (I don't go to bars with any markers, pens, etc), I think I would if I found something truly unpalatable and felt that a small addition would alter the graf in a positive way. I'm not a huge fan of marking up bathroom walls, but if it can turn a swastika into a stick figure, I'm all for it! Let's hope this kind of practise (as well as bar owners washing walls frequently) can dissuade idiots from defacing walls. I know, not likely.