My husband took up Shotokan karate after being accosted and threatened by one of the local heroin dealers and his pal. The dealer was a former pupil who still had family members at the school where DH and I both taught at the time. (Most of the men in the family have convictions by now. One of them was a wife beater and arsonist. He didn't go to prison, however, until he bit a police officer.) He had previously turned up at the school demanding to see DH because he had dared to give his son lines. (It wouldn't happen now: most secondary schools in our LA have banned teachers from issuing punishment exercises.)
In the Heidie's office, the bloke had started to jump over a desk to hit DH. DH just stepped out of his way and the Heidie told the former pupil to leave.
When accosted, DH kept calm and walked into an area where there were other people. It was a Saturday, broad daylight.
He joined the local karate club. He was in his late 50s at the time; got his black belt in his mid 60s. At the point when he got his brown belt, the dealer's daughter asked me whether that was my husband who had passed the exam for the belt. (My husband had retired by then. The results had been published in the sports page of the local paper.)
That one short article was enough to get the dealer and his family off our back. As DH said, he doubted that a man of his age would be a match for more than one of the scoundrels, but he enjoyed the training.
The club sensei always stressed that you avoided troublemakers and places where you thought that you might find troublemakers. Do your best to de-escalate, block if necessary and get away - but yes, "Better to be judged by 12 than carried by 6" was quoted.
The dealer died when he was in his early 60s. FB was full of heart-rending tributes from his extended criminal gang of a family. DH had outlived him and commented "Well, that's one worry out of the way."
The dealer had previously appeared on STV news as a "victim" of drugs. It would appear that he'd been stupid enough to try his own merchandise, so that no doubt contributed to his demise. The men in the family weren't terribly bright: one of his nephews was done for re-set after travelling out of the area to sell jewellery that he and a relative had stolen...He gave the jeweller his real name and address.