If you look at the real original Star Wars, Greedo didn't have time to shoot. Because Han isn't a retard, and knew that shooting the motherfuck was going to be his only way out. It's the exact same impulse that led him to shoot the console when the conversation with the storm trooper went south during Leia's rescue.

And he knew he was in a real, honest-to-God dirtbag bar where everyone minds their own fucking beeswax.