I agree with Gates on this; as I did a number of times, on similar occasions, when active and retired military waged public campaigns against Bush over Iraq.
The last thing the men on the front lines need to worry about is that the White House does not support their commanders or their commanders do not support the White House.
To the men and women on the front lines, they need to know their mission and the support for it runs from top to bottom and bottom to top.
If McCrystal seriously believes the White House will continue to take a wrong turn, and is not listening to him, he needs to resign (acknowledging HE lacks confidence in His leaders), await his replacement, take off his uniform and then take his position public. Until then, he is fulfilling his responsibility to the nation and his professional duty, by simply insuring his superiors have heard and understood what he has to say. Meanwhile, there are plenty of others out of uniform that, on their own, have voiced and will continue to voice the same concerns about current US-Afghan policies.
First you'd have to establish beyond a doubt that that was what McChrystal did. I'm not yet sure he did anything like that. There are a ton of motivated leakers in DC of all stripes. It might not have been the general who leaked.
In any case, though, he ought to resign his commission at the rebuke from Gates, which basically accuses McChrystal publicly of dishonorable or improper conduct.