The reason that the light switch overheats, and eventually melts is because the fog lights draw too much current through the switch. From the factory, the fog lights draw their power through the headlight switch & the current is too high which causes the switch to overheat. Ford built a heat safety into the switch which is what causes the lights to shut off & flicker...it gets too hot, and just shuts everything off.
If you do the Corral fix, you're no longer drawing the power through the headlight switch. You're running a dedicated 12g power from the battery for the foglights. The fog light switch on the dash is now only used to simply open or close the relay. The relay is now, in effect, the fog light switch.
If you just follow the directions from the Corral, it's completely safe.