A character can easily shift from 'protagonist' to 'antagonist' at a moment's notice. I think Vyreus is correct.

I also think individual players are free to draw their own conclusions about whether or not a particular character is a 'protagonist', 'antagonist' or even both. The writers can certainly try and guide people to draw certain conclusions though asking people to pretend as if genocide is a heroic act is a stretch for many and not really something the writers have any right to demand.

I believe the writers have also admitted to not having a grand plan in mind when it came to many aspects of the story. I'm a bit confused as why this is pointed out when it comes to the Garleans and Ascians but somehow Hydaelyn is pushed as 'never' being written to be an antagonist. We don't know that and many players spoke up over the years to claim that they found her to be suspicious, creepy and needlessly vague.