Well, in-universe the process is called "bleeding" and IIRC it seems to be the reason the crystal in Kylo Ren's saber is cracked forcing him to use the old-fashioned vents, he just poured a bit too much of his own negative emotions into it during the process.
If you're going to drag in the EU to prove your points, I'm out. I couldn't give a toss for any of that wank.
Never said that the movie relying so much on EU stuff wasn't a mistake but it's not one that destroys the movie for me.
Sometimes the simplest explanations are the best. For example, without the force-enhanced reflexes necessary to put your lightsaber in the path of incoming shots, maybe it doesn't make sense to bring a sword to a gun fight.
No, it totally makes more sense that you need to torture a rock.
And just to add some context here, I'm basically onboard with Star Wars as space-fantasy and the force as magic. I don't look for tons of external consistency between Star Wars and reality, nor do I feel that elements of the franchise always benefit from having a detailed explanation of their mechanics *cough* medichlorians *cough*. I just think that there's a really simple, obvious reason for randos not to favor lightsabers over blasters the way force-users do.
Torturing a crystal.... 
Lightsabers can also cut into blast doors and AT-AT armor (as shown in the movies, think of the reaction the Neimodians had in episode I, normal portable weapons aren't supposed to cut into a blast door), don't you think that even if not used for fighting most non force users would like to have one? I mean, you don't need to use the force to cut a blast door like it was a tauntaun's belly.
In the old EU kyber crystals could be
synthetized, yet only Jedi and Sith used them for *reasons*.
Also one moment the green crystal Luke used was synthetic, the other moment only Sith used synthetic crystals because all synthetized crystals were red apparently.
The new EU clarifies that Kyber crystals are rare (most of them no bigger than a fingernail) and living (albeit not sentient) emanations of the force itself, every attempt to make artificial ones failed (Jyn Erso's dad tried and failed countless times before working on the Death Star) and that you need a force user to make sure it behaves or a wildly complicated system that's too big to lug around easily and works well enough only with rarer bigger specimens (hint: the Death Star used that system, invented by Jyn Erso's dad, the empire tore up entire planets to get enough big kyber crystals to make the thing, the second Death Star reuses mostly crystals recovered from the first one's remains).
What the kyber crystals do is basically amplify the energy put into them by magic (well, "through the Force" if you prefer), but a "wild" kyber without said complicated system or a force user may randomly output nothing or blow up the amplified energy in your face (what happened to one of the first Death Star superlaser prototypes in the novel Catalyst leveling down a nearby small city).
Kyber crystals are also used to make the famous Jedi and Sith Holocrons.
He's dismissing EU as far as I can tell?
That stuff about torturing crystals sure as hell doesn't come from one of the films. So unless it's from one of the ridiculous number of Star Wars shows, where is it from?
There are only three canonical animated series, The Clone Wars, Rebels and Resistance.
The concept of bleeding was anticipated by Pablo Hidalgo but is first explicitly mentioned in the second Darth Vader Marvel comics series. The purification part comes from the novel Ahsoka, while the concept of kybers being natural and connected to the force comes indeed from the cartoon The Clone Wars and was made at Lucas' request apparently at the time the old EU canon was entirely different and he notoriously used that cartoon to retcon all the EU stuff he didn't like.
