Hmmmm..... in case you hadn't noticed, this site is a tad bit on the liberal side of the right of freedom of expression.
Actually, I had noticed, and while I was hopeful that decency might prevail in this case, I wasn't necessarily betting on it.
There are some actual No-No's outlined in the new Forum Guidelines where decency is enforced: No "Bigotry, racism, religion-bashing or aggressively homophobic language". Vulgarity didn't make this list (as such), but there is precedent for certain
vulgar language posts to be removed.
And so it could be for vulgar pictures - at the moderator's discretion, of course.