'Workaholics' -- Coast Guard Says, The Gag Over Anus is Heinous

The Coast Guard is fuming over this week's episode of "Workaholics" ... claiming a scene depicting their men forcing a dog to lick the butthole of a faux seaman has deeply offended their ranks.

In case you missed it ... "Dorm Daze" featured a scene involving actors playing Coast Guardians angrily pouring soda into the fanny of Anders Holm's character. Then they let a dog go to town.

C.G. officials fired off a letter to Viacom execs calling it reprehensible to portray military officers in such a degrading way ... and they weren't happy about the fake Guard members lining up for a porno scene.

The letter reads, "Sexual assault is a crime. It's not humorous and it's not funny," adding, "Sexual assault is a breach of our Core Values of Honor, Respect, and Devotion to Duty that each member of the U.S. Cost Guard promises to live by."

We reached out to a rep for Workaholics. So far, no word back.