Are they allowed to, yes. We have an all volunteer force, so yes they can tell you to feel free and get in front of the bullets (by quiting they re the ones standing between you and them) However an active duty service member no longer has freedom of speech, or really any freedom so no they can't say that. They can't make political or social statements especially publiclly like that.
I complete agree I think the entire military should quit on the u tied states. They get screwed and screwed and screwed again. The people of this ungrateful nation don't deserve them.