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

YOU WILL ALWAYS SHOW YOUR SUPPORT FOR THIS COUNTRY REGARDLESS OF UNIFORM OR NOT. WE HAVE FOUGHT AND DIED FOR THAT..SHOW THE RESPECT FOR THOSE WHO HAVE GIVEN FOR THAT RIGHT....

Unless regs have changed, you WILL come to attention and pay respect to the flag. It is in the job description.......

I believe any active duty reserve or guard members have taken an oath to to defend and support The Constitution. Standing during our national anthem is part of that

I believe we still have standards and regulations that we must adhere to regardless of personal beliefs.

Sure they can, provided they don't mind being Article 15'ed under the general article....

Not only no but HELL NO!!

While we do place some of our 1st amendment rights on hold during our enlistment they are not taken away. By swearing our oaths we voluntarily accept these limits, I remember discussing this topic in length during boot camp as it came up during one of the times the CC had set aside for Q&A. The only person who did not seam to accept this answer was eventually the one who went over the wall.
I look back and I find that my time of service galvanized my belief in the social contract we call the Constitution and in our country. We serve to protect that contract and as such the right of idiots to say and do things we do not agree with.
Back to the original question, No, if you wear the uniform you accept the requirements that come with it and render honors as required.
I remember being stationed in the Pensacola area and attending movies. It was still a regular thing for theaters to play the national anthem as part of the coming attractions line up. You could tell the military members as they were the ones at attention as apposed to covering their hearts or simply sitting.

If you are in the Air Force AFi 34-1201/Protocol, Chapter 2, Paragraph 2.17 specifically states what active duty members in and out of uniform are required to do.

of course not!!!!!!!!!!!!!!!!!!!!!!!!!!!

The answer is no. We have been standing, saluting and placing our hand over our heart or just standing in the direction of the flag/music for over 300 years. What's changed in the aspect of respect?