While the placement of such items is not generally prohibited, flags, banners and signs are often cleared by guard staff at the end of their shift “as a general rule,” the spokesperson added.
This sounds like a set-up to me. Unless there was a particular anniversary or something, it sounds more like a political statement. And if they never told the embassy staff, and it is normal practice to remove things like that at the end of each shift, I have zero problems with it.
The Big Mike hi-lo quote is the dog whistle give away.