Let me draw an analogy for you. You all probably know how to control a single unit, like zombies. But a player who has only played against the computer and never thought about micro-management in battles, never played online, doesn't know how to do that. And has never seen it before. So, he starts playing online and sees a stream where someone is controlling gargoyles to attack undead. But he doesn't know how to do that, and he's never seen it before. Similarly, he might get upset and think that it's exploiting a bug, that knowing the algorithm for neutral unit behavior should be banned, and that using more than 2 heroes is only done by cheaters.
And I'll repeat again, setting up units on auto-battle is not a bug; it actually fixes a bug.