Please explain to me how you would transition out of an arm bar from the guard into a mount on the subjects back and then place the subject into handcuffs
A) without exposing yourself to an attack from the subject or a bystander
B) without exposing your firearm or other weapon on your duty belt to the subject or a bystander
C) maintain compliance from the subject the entire time, without providing an opportunity to resist or escape
D) maintain control of the subject in a way that allows you to regain control immediately should resistance occur
The answer is, you can't. No one is saying cops would not benefit from BJJ, as it is, there is commonly BJJ in the defensive tactics curriculum, as a way to fight back to your feet. Cops don't like defensive tactics because they are lazy, the motivated martial artists on the force never complain about a DTAC day with pay. Despite your opinions on the subject, there's much more that goes into an arrest situation and that's why you can't drop on the ground with everyone and go for a choke or submission. IF you get taken down to the ground as a cop you are in a fight for your life immediately and are likely to be attacked by a bystander so maintaining distance and paying more attention to how you enter and receive an opponents line of attack and what you do from there is more Judo and Aikido than it is BJJ, the BJJ is in the one half percent of emergencies where you are scrabbling with someone on the ground trying to get your gun, that's it. I keep trying to explain this to you and you can't seem to understand that if you are on the ground in a fight you are literally waiting to get kicked in the head by the guys friend. Aside from this, you can't cuff a guy in a choke or submission and the moment you turn the submission off you are fighting again, you don't have the option to break the guys arm because he didn't tap.
BJJ is great, all martial arts are great, more training is more training but you have a deluded concept of how confrontations work and you can't seem to get over the fact that BJJ on its own doesn't go anywhere and isn't an end all, be all, neither is MMA sport fighting. I don't have a library of videos for you with Aikido, that doesn't change the fact that it works or that its good for these types of encounters. While I don't think it has a great future in the UFC, I also don't see the logic in discounting a martial art that gives officers a way to handle a subject while using less force and preventing harm to both parties, or why a private citizen wouldn't be well served learning the same. If your argument is "it doesn't work and therefore A/B/C" please remember, you have already had more than one LEO in here saying it works. The irony of some guys not in law enforcement lecturing people in law enforcement about what has and hasn't worked for them is absolute comedy gold on this end, personal anecdotes notwithstanding.