It was pretty obvious to me the cops knew they were not real guns of their behavior would have been much different. I talked about this in posts above on this page, but you ignored those parts of my post.
If they truly saw evidence that they were selling illegal guns they would have not said they had a complaint. They would have drawn their own weapons and proceeded to move people away from the weapons and generally took charge and i would have no real issue with that, but that is not remotely what happened.
I worked with police officers for many years and I have read a lot on the law and their procedures. I don't know everyhting by any stretch, but I am familiar.