No, he was not a trained police officer in the military, this idea that because Marines were taught hand to hand combat it means they had the same training as a police officer is simply incorrect, absurdly so. Military personnel may be trained to subdue someone with a hold, and this is one of the ways they were trained, but they are not all trained in Law Enforcement tactics. It is unusual for this particular hold to end the way it did. As I noted, even the prosecutor in NYC where they overcharge crimes in the hopes they'll get a plea deal, knew he had no basis to say it was his purpose.
Anyway, the standard will be "reasonable person" as he is not Law Enforcement any more than you are.