I'm fine with footwork and lateral movement if you are doing it at a fast pace - I'm even OK with dashing out of range so long as you are facing your opponent. For a good example of this, see Dodson vs Lineker - although he's constantly darting out of range, he's facing his opponent.
Freeze frame Gus, and you can literally see a scene from a street chase. He is in a full stride run, back to his opponent, literally running away from the action.
This would never stand in boxing, and it has no place in MMA. It is timidity and at best skirting the rules. I'm a big fan of Gus, have been for years, search my post history.
What he did was awful, and its bad for the sport if it becomes more commonplace.