I think the point is, that you should always be careful about what you post on the internet. While it seems to be anonymous, it's really not. If something would happen in the future, someone could research his history and find a pattern of disregard for the law if he had made several posts like this.
It comes down to it being really stupid to admitting to breaking the law or anything else that may come back to bite you on the internet. The internet/facebook/twitter is a divorce atty/prosecutor/private investigators best friend and it's only because people think they need to post their entire lives online.
I could be wrong but I don't think you can be arrested simply for saying that you broke a law without there being some other evidence to back that claim up.
If that were true then every comedian who ever claimed to have smoked pot in their act would have been arrested for drug use.
That's not the real problem here, though. I still say it's childish to break a law then brag about it "anonymously" & unsolicited on the internet. Especially when there was a legal alternative (OC outside your vehicle while walking those "mean streets") that is inline with the 2A which was why the OP said he decided to break the "unConstitutional" law in the first place.