What is the policy for military members publicly criticizing the President?

No it's not okay. I was told the same thing and during 35 years of honorable service, I respected the Office of the President and the Commander-in-Chief. I did so regardless of whether or not I voted for him or if I agreed or disagreed with his agenda. After President Obama was elected, people I had served with for years suddenly decided it was okay to openly denounce a president's character and/or his policies. Particularly those about women in combat, gays openly serving in the military and the ACA, so anyone who thinks this type of behavior started under President Trump has a convenient or selective memory. In fact, during the Obama administration a General Officer was recalled to Washington and forced to retire for making public comments in opposition of the administration. I'll say here what I told my troops then. I don't give a rat's ass if you disagree with the administration, we are here to execute policy, not create it. Most importantly, we swore an oath to uphold the Constitution. Vote for who you want and campaign for or support who you want during your off-duty hours. When on duty keep your damn pie hole shut. It's time we got back to some regular order and discipline.

Revision: After a member retires or otherwise separates from service, they have as much of a right to criticize the President as anyone else. As far as being disrespectful goes, I would say you get what you give. In my opinion candidate Trump disrespected a sitting U.S. Senator, who was a retired naval officer and former POW, before he even held office.

Maybe Douglas MacArthur, James Mattis, or John Kelly will weigh in on this. Seriously, though, for all the complaints about Trump's "thin skin," he has been remarkably tolerant of the vituperation heaped upon him.

I suspect many of us critical of the president elect, the left in general and of a Christian conservative bent are going to find out when Big Tech and the DOJ finish their review of our social media footprint. . . .

The UCMJ prohibits serving officers from using "contemptuous words against the President, the Vice President, Congress, the Secretary of Defense, the Secretary of a military department, the Secretary of Homeland Security. . . ." (Art. 88, UCMJ). An enlisted member would be charged under the general article, art. 134.

But the UCMJ doesn't apply to reservists who are not on duty. So reservists can do so to their hearts content.