"Could sophisticated military tanks and anti-aircraft missiles given or sold to countries like Iraq be equipped with a way to disable them if they're compromised, without opening them up to hacking by an enemy?"
No. Of course not. If you can destroy or disable your own equipment remotely then it's only a matter of time before someone else figures out how to use or break that function on their own,.
A much better approach would be to put a little red button on the bottom of everything and let nature take its course.
"I hate warriors, too narrow-minded. I'll tell you what I do like though: a killer, a dyed-in-the-wool killer. Cold blooded, clean, methodical and thorough. Now a real killer, when he picked up the ZF-1, would've immediately asked about the little red button on the bottom of the gun."