(Oops! I accidentally locked this!)
The premise of the article is correct, we can't expect to be able to order police to commit suicide. This applies in other ways, too. If the police were to be ordered to go door to door confiscating firearms, most would refuse to do it, not necessarily because it's unconstitutional, but because they're liable to get shot (or be forced to kill) trying to do it.
Sometimes people forget exactly why the redcoats were coming back in Paul Revere's day. They wanted to confiscate the guns of Colonials in Lexington and Concord.