Did you actually look at the article posted in this thread? Whether or not you agree is one thing, but there is certainly evidence that weapon appearance can sway juror opinions.
Shooting someone is against the law in every jurisdiction in the United States. Whether or not you have a viable affirmative defense is only rarely required to be considered in the probable cause determination. Even in those states where it is required, it's questionable how this should actually be applied by a court.
Also, you've articulated the standard for reasonable suspicion, not probable cause.