No. If you stay and refuse to follow unlawful and unconstitutional orders, that does not make you a fascist and is a far more effective strategy than allowing your power to be usurped by actual fascists.

That is not the way it works at all.

If you stay in a position where you support fascist regime that makes you a fascist.

Being in the military doesn't make you a "supporter of a fascist regime". It puts you in a position to stop fascism some day. The Romanian dictator was executed in 1989 by his own military.

If you stay on “to prevent things from getting even worse” that will not fly at your eventual court hearing.

Those people aren't going to have an "eventual court hearing". They are going to have a court hearing for every officer in the US military? Don't be ridiculous.

Also, if they replace all the competent people with sycophantic morons, eventually the whole thing will collapse.

This is so naive. The Bolsheviks in Russia lasted from 1917 to 1991. China's dictatorship started in 1949 and is still going strong. More likely than not a dictatorship will last for the rest of your lifetime.

An officer commands a unit. That officer can order troops to deploy to protect citizens.