Like everything I say it was mostly snark, containing a little diamond of truth.
But, in plain language- Cocks on posters freak people out. Look at the reaction. They make people genuinely uncomfortable. Boobs don't do that. Blood doesn't do that. And many a masters' thesis could be written on why that is.
But the point is, noise bands and the culture around them have always gravitated to the most shocking, squirm-inducing imagery they can find, because it's what they imagine they are doing with their music. It's a wedge. You're either into it, in which case you're "one of us", or you're "shocked" by it, in which case fuck you you're a tool.
Look at the covers to Japanoise records. Lots of cocks. Lots of sadism. lots of pedophilia. lots of rape.
I like this poster much more because it seems to be a representation of all the potential fun aspects of noise- spontaneity, un-inhibition, freaking out, getting naked.