I think this is a huge overreaction to a valid concern, and it has more to do with people wanting to find some explanation for the Horde's sudden narrative (mis)direction.
The idea that this is all fueled by some guy's Gary Stu having a crush on Sylv, and that she will commit bad girl acts and be immune to any retribution as this writer hugs his Sylvansas Bodypillow, crying and screaming that we cannot hurt his precious Queen *DOES* seem plausible and would explain that the Battle for Azeroth is really some wank fantasy forced upon us.
But there is a huge overreaction to this. He doesn't need to be fired, but maybe we need to have a writer who has no real vested interest in Alliance or Horde actually help steer this narrative ship? Some objectiveness could be good here.