This is not always the case. Builds like Twisting Blades Rogue that use Puncture require almost non stop clicking at every enemy encounter. The accessibility features will only prioritize the button that is pressed first and will not alternate between two buttons if they are held down simultaneously (which it should).
Additionally, I would wager that this fellow was not banned for just using autohotkey, but rather experimenting with a few bots. I can’t name names here, but some people were quick to push out bots (for money, of course), and Blizzard took swift action to ban these accounts. As far as I’m aware, there have been a couple ban waves already.
Blizzard is extremely unforgiving with the use of third party software and will permanently ban accounts with no warning the moment the hint of evidence arises-- That should be known to anyone who experiments using any such software.