I think an important distinction is that he wasn't making generalized comments about school shootings. There's nothing satirical about what he says and he's not framing a punchline or joke.
He specifically lambastes survivors (children) of a school shooting standing before congress and directs vitriol towards them standing there as if it was a publicity stunt:
I don't know, they testify in front of Congress, these kids. I mean, what the fuck? What are you doing? You're young, you should be crazy, you should be unhinged. They're in suits saying "I'm here to tell you..." Fuck you, you're not interesting because you went to a high school where kids got shot. Why does that mean I have to listen to you? You didn't get shot — you pushed some fat kid in the way, and now I've gotta listen to you talking?
This is shit I'd fuckin' read on my crazy ass aunt's facebook.
And then he follows it up with lame ass whataboutisms that you see only from the edgiest of posters:
So that day 17 got shot in a school. What about the other 7,500 people? They didn't die in their sleep… People get upset that they're young, they died so young. That's offensive to me. What, if I die now, fuck me?
Old ass angry dude rambling, that's all this bullshit is. He ain't workshopping. He's just an old, angry, perverted asshole.