So the story is nice but you are talking about speakers and this has been about how @Over_clox wrongly stated that plugging that guitar into an amp would blow the amp or shock the player. The guitar itself can't shock anyone or destroy any equipment it is plugged into.
If a faulty amp with a bad ground causes a shock through the guitar, it is from the amp and passed through the guitar. So the cause of the problem and the shock is the amp. Not the guitar.
If an amp is dialed to 10 and you plug in a guitar and play a chord and blow the speakers, did the chord you play come through so loud that it blew the speakers? Nope! The amp is driving the speakers past what they can handle. Again not the guitars fault. Same could be said about scratchy pots, switches, etc.
But let's bring this back to the thread, OP was given an Epiphone Les Paul Pro. Someone assumed it was wet and had corrosion. The oxidation on the pickups and parts are normal for gold hardware from Epiphone. Having a 5w practice amp to test would be more than enough. Cause again, the guitar isn't shocking anyone or destroying any amps!
Can amps shock you or break speakers? Yes. But in in your speaker example you didn't get shocked. The amp didn't even break. The speakers did and it was due to human error. Those crackles didn't damage anything until it was at full volume.