He quietly urged other military personnel to reflect on their own positions. “They should be confident in questioning possibly immoral or illegal orders,” he said, “remembering they are responsible for their own actions, and knowing others are asking the same questions.”
“If they have doubts about their orders, they are not alone,”
People in his command see this. Shit, we see this here. But his resigning has an impression on people, which may unfortunately be the only effect he can make. The whole unlawful orders thing is a sticky situation at best, and what all of us here in this tiny echo chamber believe is not what is reflected in the real world, and so some stand he may take may end up unseen and unheard while he rots away as an O-1 in Leavenworth.
Same with when Mattis was fired back in term one. Sometimes the only statement you can make is your resignation.