This happened to me, and I did something about it.
Cycling along, a chav leaned out of the passenger window of a chavmobile and sprayed me with some unknown liquid. Initially I was livid, but wrote it off as the car sped away and I assumed I would never see them again.
Couple of minutes later I spotted said culprits stuck in traffic at a T junction with a learner at the front who was a bit hesitant pulling out.
If you've ever seen a terrier get sight of a rabbit, well that was me, I was motoring (well, cycling - fast).
As I approached the car,the front seat passenger had already caught sight of me and was quickly winding the window up, and also the traffic was starting to flow again. In a moment of madness/red mist, I simply stuck my right elbow right through the windscreen. This is where it all goes wrong. Although the car was full of chavvy boys, the driver was in fact the daughter of a friend of ours, she went mental, tears, dialled 999 etc. 3 police cars and an ambulance turned up, I was frisked and handcuffed, arrested - the full works. There's more - all this happened outside my front door! My kids all popped their heads out of the front door, all the neighbour's suddenly found things to do in the front garden - talk about making an ass of myself.
Anyway, managed to get away with an on the spot fine in the end, although the chavs just got a slap on the wrists.
The moral of the story - watch the red mist, and don't screw up in your own neighbourhood.
Have I learnt my lesson? I really don't know. i'd like to think so, but I have great difficulty accepting that idiots like these are allowed to get away with this type of behaviuor without any repercussions. Anyway I'm keeping my head low for a bit.