Good for General Dempsey! The Chairman of the Joint Chiefs of Staff warned military officers, including retirees, to "remain apolitical."
There are legal limits on what active duty personnel can do politically: they can vote, but not endorse candidates publicly or appear in uniform at rallies. Retirees are not prohibited from openly supporting candidates, but their advocacy can be seen as institutional support.
Both parties have trotted out their four-star celebrities, with the Democrats probably doing more than the Republicans because of their perceived anti-military feelings, probably a legacy of the Vietnam war.
It's bad. It shouldn't happen, And the retirees should not politicize the military by engaging in such activities.