You’re only partly correct. The CinC is the only civilian that ranks a salute from members of the military. And while no law or rule, as you call it, requires him to return the salute, custom certainly does. And custom requires that it not be half-hearted or half-assed. Hell, even Boner Bill, with his admitted loathing of the military, never did anything as lame as return a salute with a cup of coffee in his hand....
Sorry, but there is no historical custom for this.
1981 does not a custom begin.
I agree if you are going to do it, do it right, but hardly is this some insane breach or protocol or responsibility.
The guys an idiot, everyone knows he’s an idiot, and of all the dumb things he’s done this is beyond trivial.. but its nice red meat for people who are going to get upset about anything he does instead of the real stupid stuff he is doing in the world that is likely to cost their kids and grandkids.
This is just white noise.