I believe the first thing that might have triggered an armed robber to attack someone and demand a transfer of their coin is if the armed robber knows that the person been attacked is a bitcoin or crypto trader. This is why it is recommended that you live low key if you are trader especially one with huge fund. iluvbitcoins suggestion is perfect but what if you where not at home when the incident happens and was attacked when you least expect it; probably when you are out for a quick dinner? I guess its better not to have a trading app on your phone and live a low key Life till when you decided not to trade again. Though, most people may not like it since they want to live a five star life when the gains start pouring in.
Keep the cold wallet at home encrypted and only a hot wallet with you, therefore if someone attacks you, if you're forced to, you can give away a low amount of coins.
I'm unsure how it works in the US, but if it's possible, get a legal carry, if not, as I said, pepper spray, electric shocker, or a knife.
I'll be getting a new batch of bitcoin knives soon, might as well get those
sigh... Some of us live in countries where it's illegal for an individual to carry any kind of firearm (unless traveling from home to a shooting club or back, carrying a legal licence, with the gun locked up in the trunk), any kind of gas pistol, pepper spray, knives, tasers, baseball bats,... Basically, it's illegal to carry anything you can use to protect yourself
Personally, i recently hired a safe at our local bank to store my hardware wallet (+ the encrypted seed). I don't own that much BTC anyways, but i was entertaining the idear of renting a safe to store my house's deed, my testament, some silver coins,... so when BTC price jumped, i just hired a safe and got it over with.