It wouldn’t be an issue if Baine hasn’t been written for years as an Alliance character who puts the Alliance first.
When was the last time Baine ever did something in the Horde’s interest, even if it inconvenienced the Alliance? Has he EVER? Has he ever had so much as a harsh word for the Alliance or anything it has ever done?
He’s a poor substitute for his father, who was a beloved Horde lore character that Blizzard offed just to satisfy their bloodlust for a Horde NPC body count.