Should Military (Active Duty, Reservist & Guard) be allowed to "sit", in support of personal beliefs, during the National Anthem?

That's an activity best left to those not wearing the uniform.

According to Title 36 U.S. Code, Chapter 10, Paragraph 171, "During rendition of the national anthem when the flag is displayed, all present except those in uniform should stand at attention facing the flag with the right hand over the heart. Men not in uniform should remove their headdress with their right hand and hold it at the left shoulder, the hand being over the heart. Persons in uniform should render the military salute at the first note of the anthem and retain this position until the last note. When the flag is not displayed, those present should face toward the music and act in the same manner they would if the flag were displayed there.". In the military, our job is to protect democracy, not practice it.

No.

Whether you are in uniform or out of uniform a veteran, active duty service member or civilian the only thing that matters is if you are a US Citizen and if you are then don't break the law especially to advance your cause. I guess nobody remembers that the United States Code establishes what is to occur while our nations anthem is played. So why are we not doing our duty in having the team owners, the media and our politicians have these activists stop breaking the law to advance some cause? For anyone not familiar with The United States Code it is a consolidation and codification by subject matter of the general and permanent laws of the United States. It is prepared by the Office of the Law Revision Counsel of the United States House of Representatives and you can see for yourself by going to U.S. Code Title 36 Subtitle I Part A Chapter 3 § 301:
36 U.S. Code § 301 - National anthem
(a)Designation.—
The composition consisting of the words and music known as the Star-Spangled Banner is the national anthem.
(b)Conduct During Playing.—During a rendition of the national anthem—
(1) when the flag is displayed—
(A) individuals in uniform should give the military salute at the first note of the anthem and maintain that position until the last note;
(B) members of the Armed Forces and veterans who are present but not in uniform may render the military salute in the manner provided for individuals in uniform; and
(C) all other persons present should face the flag and stand at attention with their right hand over the heart, and men not in uniform, if applicable, should remove their headdress with their right hand and hold it at the left shoulder, the hand being over the heart; and
(2) when the flag is not displayed, all present should face toward the music and act in the same manner they would if the flag were displayed.

I still salute the ensign in plain clothes.

If they are in uniform, they represent the military and the Nation. They absolutely had better stand and salute.

When in uniform you are not representing yourself but the organization you belong too.

Customs and courtesies who are you ppl in the military these days smh

Lmao is this a fucking joke read the order

No, of course not. When you take the Oath of Enlistment, or the officers' equivalent, you subscribe to the Army Values. Your personal beliefs no longer matter. When you join an organization of your own free will, you must adopt that organization's ethical code. That does not impact your own morality, that is your own personal sense of right and wrong while ethics is the organizational norms.