I suppose it has to be looked at from both sides. If you don't care for the CEO particularly, then you might think such 'purges' outrageous, but the 'retirees' may well have been guilty of disloyalty in some way.
Doesn't matter where in the military food chain you sit - you follow orders. If you don't, you're either fired or attend a Courts Martial.
An overt political difference of opinion on strategic issues could translate to 'disloyalty' given credence to a potential lack of trust which could get messy in the field, so, the guy has to go.
When you say "POTUS is firing everyone in the Military that doesn't agree with him", that's one issue but if you said that same sentence and qualified it by saying that they were fired for not obeying orders, that's quite different surely?
They could also be part if a group of card carrying Ku Klux Klan members, or members of the same Masonic Lodge. Who knows for sure?
Sorry, just playing devil's advocate here.