Obviously you can't see both sides, because you're still stuck on "is downloading a free game given away by the creators and right-holders of that game piracy?" with the answer being "Of course it isn't, are you daft?"
The argument is whether it is a dick move for the developers to call the people who downloaded the free version they gave away "pirates" of their game as part of a publicity stunt. I say it is a dick move and I won't support developers who would do that.
I did not personally download any version of their game.