This does in fact count as NSFW in every workplace I've ever been in. Perhaps stop trying to argue with the poster who was merely trying to give people a friendly warning just so they know they might get in trouble if someone sees them looking at this art at work.

Whether the standards of workplaces should allow artistic nudity is completely beside the point. Neither you, nor I, nor Dalewyn control such things. All we can do is work around them.