The breaker is there to protect against faults, not someone intentionally violating what it is protecting against.
That being said, you should never intentionally rely on a safety feature to cut you out - they exist as a backup in case you screw up. The 14-50P to 5-15P adapter referred to by GP is an example of "I know what I'm doing". Just be sure to double check that you really do.
Edit: Also, consider that if you're in a jurisdiction where it's legal to have a 15 amp receptacle on a 20 amp circuit (many places in the US unfortunately) then a cable like this could allow you to draw a sustained current above what the receptacle is rated for but below what would trip the breaker. That's a fire hazard.
15amp receptacles sold in the US are 20 amp passthrough.
So it is common practice and completely reasonable and safe to put 15amp outlet receptacles on a 20amp circuit because the 15amp receptacle cannot accept a physical 20amp plug.
It is NEC Compliant unless the receptacle is the only receptacle in the 20amp circuit - see "210.21 Outlet Devices".
In that case I guess the cable that triggered the article in the first place is no more dangerous than (for example) the 8 receptacles in my bedroom, all on the same circuit (15 amp IIRC). It's a complete non-issue.
Edit: Are the plug and cable guaranteed to be able to handle 20 amps though? From the pictures in the article, it appears someone spliced a 20 amp receptacle onto a typical (maybe not even 15 amp?) PC power cord.
You CAN have a hypothetical 5A plug on a hypothetical 50A circuit. The plug is instructive to the user NOT to pass more than 5A through it, and since the circuit is rated at max 50A, it will not cause a fire at 5A from the abiding user.
In this RV case, you are putting a hypothetical {30,50}A plug on a {15,20}A circuit (VERY BAD!) using this unsafe adapter. Your RV can EASILY exceed the maximum rated amps through this plug (since that is how it is DESIGNED -- with a special plug to set this high-current expectation which shouldn't be intentionally defeated to protect against this user "stupidity") and it CAN and WILL start a fire if someone uses this dangerous adapter, the AC kicks on, and the breaker fails or is not installed properly.
This situation is analogous to cheater plugs. I used a cheater plug with a Macbook Pro in a house with only two-prong outlets, and the aluminium shell felt tingly, but the house electrical system and the circuit design of the laptop motherboard, the chassis design, and SMPS in the charger still DO have other ways of protecting my life from electocution by preventing the chassis from unexpectedly shorting with AC line voltage, even without a proper ground. If these fail, I am dead. Regardless, I was admittedly an idiot for circumventing one safety system to intentionally fallback on others, which weren't necessarily designed to protect against my own idiocy since the assumption was that there is a proper ground.
* FWIW, I have friends in my hometown that are electricians, I helped my dad (properly) wire our basement, and I have an electrical engineering degree myself.
I've had to use core drills with inline (inbuilt) RCDs while hanging off rope. Those things draw ludicrous current, and are water lubricated with open thermal ventilation for the motor. It's a given that they trip out.
Unfortunately, as soon as a safety feature is regarded as reliable, it's incorporated into standard operating procedures. See Erlang for a well executed version of this idea!
Right, that was my point. Of course, a user-induced intentional overcurrent situation will cause the breaker to flip.
However, to my original point, thoughtlessly relying on a backup safety feature in this case to protect against intentional cases is something that engineers working on the Therac-25 cancer treatment radiation therapy machine did, which ended up killing several people.
The software could be set by the user in the UI to enter a bad state where the high power radiation beam was not collimated (it ALWAYS should be diffused in this high power mode). The software was left this way because there was a hardware interlock to protect against this bad state.
Then, the hardware interlocks that were thoughtlessly removed in the new hardware release (without changing the software code), causing a lot of people to be unintentionally irradiated with deadly doses -- since the engineers originally relied on the "breaker" being there, and then it was removed and/or did not always function properly.
You can look at pilot safety procedures and checks to see how this mentality is properly put into practice. Nothing is taken for granted.
It doesn't care why that's happening, and it shouldn't.
The cable has no way to intentionally violate the breaker: if you try to pull 20 amps out of a 15 amp breaker, it will trip.
https://en.wikipedia.org/wiki/Circuit_breaker
I don't believe this is up for discussion: the circuit breaker is a device that is designed and used to protect a circuit against fault conditions. That's the whole point of their use: if a fault condition is detected, the circuit breaker breaks the circuit to about the fault to propagate or damage the circuit and/or any device connected to it.
That is a fault