How about doing a little research?

According to the U.S. State Department's Chief Diversity Officer John Robinson, use of the phrase "hold down the fort" is offensive to Native Americans. The correct phrase is "hold the fort" but so many say "hold down the fort" that I won't fault Mr. Robinson for this little slip. His failing in the writing the article is worse: He doesn't know what he's talking about.
 First, Mr. Robinson's conclusion is based on nothing more than his woefully inadequate education. Mr. Robinson says that the phrase originated in the U.S.'s war against the Native Americans; therefore, the phrase is offensive to Native Americans.
Mr. Robinson's conclusion is based on a couple of facts: (1) The U.S. Army fought the Native Americans in the West; and (2) the Army built forts throughout the west as part of its war. So, "hold the fort" or "hold down the fort" must have originated  in America's war against the Native Americans and it must surely offend  today's Native Americans.
The second point is that forts pre-date America's battles with the Native Americans; and shocking as it might seem, pre-date the discovery of America. So, maybe the phrase pre-dates the war against the Native Americans in the West. Here is where a little effort on Mr. Robinson's part might have proven beneficial.
The phrase is rumored to have come about as a result of a message General Sherman sent by use of semaphores to a strong-hold at  Allatoona Pass in Georgia during the Civil War. The legend is that Sherman told the commander to "hold the fort." Although Sherman sent a message via semaphores, he denied he used this specific phrase. But the message was the same. Stories about Sherman's use of the phrase, however, led to the writing in 1870 of a Christian hymn of the same name. Here are the first two verses of the 1870 hymn:

Ho, my comrades, see the signal,
Waving in the sky!
Reinforcements now appearing,
Victory is nigh.

"Hold the fort, for I am coming,"
Jesus signals still;
Wave the answer back to heaven,
By thy grace we will."

             * * *
You can read the words here. You can read the overpaid Robinson's article here. 

Because Mr. Robinson doesn't let facts stand in his way of combating what he perceives as offensive language, he goes on to attack the phrase "rule of thumb." He tells his readers (and here I'm making an assumption) that the phrase has its origins in domestic violence. Robinson believes that the law in England once allowed a man to beat his wife if the circumference of the rod was not greater than the husband's thumb. There's no proof that this was ever the law in England. Here is a little more information Mr. Robinson failed to consider. The thumb has a history of being used for various ways of measuring. So, the phrase most likely is attributable to the history of measurement and not domestic violence.