"Why do some people constantly lean on the tired, shabby argument that only people with first hand experience in any given situation can possibly have an opinion?"

Probably because there always seems to be a lot of uninformed laymen chiming in to critique the actions of trained and experienced professionals.  Your only knowledge of policing comes from what you've seen on TV shows and in movies while sitting on your rotund backside in a comfy chair, but yet you arrogantly criticize their performance while they were under fire.