You really can just condense the entire argument down to this. Discussions about pay to win, bots, retail, gaming culture, mage boosts etc are all just fluff. The fundamental disagreement is whether BC includes 1-58 or not. Certainly from a historical perspective it did, BC added around 4M new players to WoW all of which had to start at level 1 and during the lifetime of BC new content was added to 1-58 (Dustwallow Marsh completely revamped, new quests added to other 1-58 zones, etc)
Blizzard however has decided that BC Classic will be different from actual BC in this regard. In their own words
There’s really no point dancing around other topics related to the boost. This is what people are disagreeing on, and Blizzard has stated their stance.