In this context, bathroom stall graffiti would be lewd limericks and the like. Tagging is different. But also it's just a joke.

I think the joke claimed to make a real point, and it's totally fair to critize that point.

We're going to have to collect data on the ratio of bathroom graffiti between tags and limericks. Anecdotally, where I live a it's mostly silly goosery.

Just to be totally clear, here is an example. Please cover up my user name for an authentic experience.

A dozen, a gross, and a score, Plus three times the square root of four, Divided by seven, Plus five times eleven, Is nine squared, and not a bit more.

Over half a century later it still rings clear as a bell ...

    He who writes on bathroom walls
    rolls their shit in little balls.

    He who reads these lines of whit
    eats these little balls of shit.

A little cynical of the arts isn't it.

it's like bragging you're Spartacus