I approve of this!
Personally I am a big believer that people should be able to enjoy themselves and do thing things in as much of a controlled environment as possible. Life is too short to spend the whole time worrying. As the OP has stated, there was no chance of anyone being hurt when this was done, so at the end of the day who is affected? The only person who is affected from this is the person who has to look at the sweet lines that were drawn, which the OP has tried to find a way to clean off. People do silly things in cars, it's a fact of life (and a definite fact/rule of any forum like this.... especially AE86DC), any one who denies this is nieve. As long as the people are trying to do it as safely as possible and no one gets hurt what is the problem (it's the whole "if a tree falls in the wood, does it make a sound type argument).
How can we avoid this sort of thing in the future? Give people a chance to do this in a legal/controlled environment! As long as there are cars, there will be people who want to drive them to their full capability (most cars on the road capable of 50-100% more than their owners actually believe)! Yes, this means that there may be risks and accidents, but if people try to do this properly and are given a decent chance (not one potential track day that costs $500 every two years) then it won't be a big issue.