The part that amuses me is that the Cerne Abbas giant is probably not all that ancient at all. You see, just down the road from him there was a monastery full of deeply religious, easily offended monks who had a penchant for writing things down. We still have much of their monastic record-keeping, and though the records detail much minutae over money, local events and local features, nowhere is a priapic graven image upon a local hill mentioned.
The best guess is that it dates to the Civil War era, or just after cessation of hostilities and is intended as a caricature of Oliver Cromwell, for the amusement of local closet Royalists; it depicts a hugely masculine figure of great and primitive power (which Cromwell was, not that he ever wanted to admit it) which was probably a laugh a minute locally.
Well, you had to make your own amusement back then.
Seen in that light, Homer Simpson is really quite a good companion for the giant; a bit lacking in the crude humour department but pretty good nonetheless.
What a pity the Pagans don't seem able to laugh at the joke.