Huge tizzy at The Capital Sun, the local Naturists' newsletter: The U.S. Fish and Wildlife Service is braced to ban nude sunbathing on the Virginia stretch of Assateague Island. (Unless you're a Fish or Wildlife, natch. Don't let's overdo.) Meanwhile, the Nude Community is cautiously de-togging for the National Nude Weekend, coming right up. The Sun dishes very detailed instructions on bug-repellent, hats, suntan lotion, and not offending the Less Liberated. Ear likes the bit that says, "We were lucky last year, even had a favorable wind." Favorable for what, oh Lord? . . . And a Fun Flash from McLean's choice snipperie, "For Hair Only." (It's where Media Marvies like Roger Mudd and weather-wise Gordon Barnes get their topiary trimmed.) It will turn over its entire proceeds from July 16 to the Wolf Trap re-do . . . And Armistead Maupin, the very wicked scribe and author of the seedily-saucy San Francisco soapie book "Further Tales of the City," is swooping through town today book-pushing. Don't swarm the haute hotels waggling autograph books, please. He's lodging in luxe at Anderson House, the severely high-toned HQ of the Society of the Cincinnati on Mass Ave. His Papa, you see, is past-president general of the Society. Ear is slightly disillusioned.