First of all, that last video you linked to isn't Columbine. It's a movie called "Zero Day," as can be seen in the comments of the video. It was made as a way to show what it might have been like during the shooting. It is fake in every way.
That all said, it is a very disturbing video indeed, despite being fictional. It really does highlight how cold and calculated and intensly harrowing that day could have been.
(For the record, I read up on lots of things about Columbine a few weeks ago. ... I don't know why I did either).
Secondly, the problem with everything you are saying is that "well they were treated so badly and driven to that."
No they
weren't, and the second you say that, you are victimizing them and, in a very small way, giving them tiny (although weak) justification. 'Cuz if they hadn't died that day and went to trial, their defense lawyers would have fired that out at every second - "These boys underwent trauma for years from their cruel mistreatement by their peers." I'm sure they'd have tried (and maybe have gotten off with) an insanity plea.
That said, what drove them was anger.
Pure anger and hatred. And that is the problem here - they couldn't handle their own anger. Their journals were just publically released, and in them, they talk about hating the world and how "Hitler had a final solution, but it wasn't big enough. Our final solution is to KILL HUMANITY."
Note the KILL HUMANITY, which they wrought in large capitals. (You can look this up if you want.)
They were disturbed far beyond hating their school mates, and if they had thought it through, I'm sure they would have planned something much worse.
Tell me, do you know what really was meant to happen at Columbine? Originally they were going to level half the school with propane bombs (sorry Hank), killing hundreds instantly, and then walk around after the ensuring chaos and pick people off. But the bombs didn't go off, so they went in commando style. Again, their journals confirm all of this, citing "we want to outdo Oklahoma City [bombing]."
What does that say to you? Does it say a few insults from the football team (another interesting side note - research suggests they weren't nearly as mistreated as the media reported, and weren't members of the Trenchcoat Mafia) suddenly make you hate humanity?
No, you hate humanity because you are
ed up.
How you reach that state of

ed up is questionable, but I highly doubt it is purely from the snotnosed beasts any nerd deals with on a regular day, and subsequently feels sorry for in their career and adult life, when those same assholes end up washing your car for a living.
That isn't to say those kids weren't depressed and miserable. They obviously were. But above all else, they were angry, and they apparently thought they had few outlets for sanctuary and rescue.
But they did, and that's the problem entirely.
It's a simple equation here - angry kids. They just were pent up and frustrated and riding an angsty hardon all the way to their suicides.
Look, I hated high school as well. Had few friends and didn't see much of a way out. But at no point in my mind did it ever occur to me that maybe I ought to take care of business at the end of an illegally obtained and illegally modified rifle.
Instead I had to find other solutions, however good or bad they were, but I found them, and they were more than adequate.
What Klebold and Harris manifest is not a backlash against schools, it's a backlash against things like anger and unchecked rage. It's the same thing that makes a guy get out of his car and rush hour and splatter some brains.
Here's the deal - this shit is insane and I have no idea why it is going on right now. But it is not because of mopey teenages being picked on. It's for a lot of other levels of mental disturbedness, and unfortunately there's very little you can do to change or fix that unless you catch it early.
At the least, Columbine woke a few people the

up out of this idyllic 1950's Leave it to Beaver bullshit they thought school days are. But we're not in that bullshit situation anymore.
I don't know what the answer is here, but it is not telling people to be nice to everyone, 'cuz there's always going to be some batshit insane

er who is going to want to hurt and kill people for no reason, and will use anything to ignite that dangerously short fuse. Even if everyone was nice to everyone and we lived in Neverland, there'd still be a Captain Hook.
So I don't know the answer. But I do know that these school shootings aren't the product of someone being called a $$$$$$ all the time, and I know the answer is a far more elusive prospect than some quick fix reactions.
You say to stop the hatred? That's the answer.
But guess where that comes from?
Within.