There is precedent when it comes to the automation of people's jobs (truckers, cab drivers, courier services) and fanatical condemnation of technological advancement; see everything from the Luddite's infamous wooden shoes to the spiking of trees to stop logging.

In the forests near my hometown, some environmental fanatics will string up wire across motorcycle and ATV tracks, or create blockages and attack riders with crowbars and pipes. I wish I were kidding.

As for current graffiti artists - they're taking down stop signs and road markers, defacing handicapped parking signs with stickers, tagging any and all road signs, and so forth. They're minor nuisances for human drivers, who can usually easily identify compensate for such changes. Computers, even those running neural networks, are not able to compensate so easily.