How in heaven's name would you know this? Big assumption..... Not everyone carrying is an idiot and untrained in the proper use of firearms in self defense.
Common sense.
Ask any police officer if he would walk around a table full of drunk Crips or Bloods with a holstered gun.
Do you think a fifty something’s reflexes are as good as a twenty year olds?
You do realize that at every second of his little jaunt his back had to be exposed to one of them.
Do you think members of MS-13 would have warned him before plunging a knife in his back and give him a chance to draw first?
Training is not a substitute for brains. Like I said, even a trained police officer would not have done what he did had they been suspected gang members.
If you're willing to take on 7 adversaries at contact distance by yourself, it's clear you have had no training.