Complaining about people giving victims of a school massacre a voice isn't actually a joke. It is a complaint.
well i do hate to keep harping on this, but you keep doing it so i have to keep correcting you until you get it through your head that you're factually wrong.
in the context of the bit, he wasn't complaining about that - trying to assert that's what happened is simply inaccurate.
i don't know how many times that needs to be repeated before some kind of understanding comes across, because it seems really easy to grasp to me.
https://www.youtube.com/watch?v=WS13C0VUiQY
the bit starts at 20:05, the bit ends at 26:00
context abridged (not a ver batim transcript but the gist):
the relevant bit starts with:
my kids are teenagers now and they i'm an asshole, and it really makes me feel like all the time and effort i put into loving them and raising them was wasted, because none of it matters to them or how they feel about me now.
my daughter said to me the other day: "no offence daddy but i just don't think it's very cool to go in a room and tell people jokes" and i was like "... well what the fuck have YOU done that makes you so interesting? you're 13, you've done nothing, the most interesting thing about is the fact your father is a stand-up comedian."
... then he talks about his other daughter and how smart she is, and how even if she was doing drugs he wouldn't know because she has her shit together so much more than he did at that age and he no idea how to compare his experience to hers. this leads into a monologue about what an idiot he was as a teenager and all the stupid shit he and his friends would do to kill time.
then he goes off about how now that he's 51 he was looking forward to seeing what young people these days are up to and what kind of crazy shit they'd be doing with new technology and drugs, but to his chagrin kids these days are boring and tame - this goes into a bit of a side-bar about "PC" topics but it's clearly in a mocking "old man yells at cloud" manner.
this bridges into an offhand comment about how kids should be wild and unhinged, not wearing a suit on CNN... and how people die every day so shootings aren't that interesting and doesn't make you notable or someone to be listened to.
(side note: in the context of his career CK has had a running theme of celebrity worship and how he doesn't believe in granting respect to people who haven't done anything notable to earn it, especially denigrating those who gain fame by circumstance)
the entire 'bit' about teens and such is around 6 minutes long. the references to parkland take up exactly 35 seconds.
so, again, comedy is subjective and i won't argue about whether or not the bit is *funny* to you, it's clearly not and that's fine.
but it's just as clearly a joke as part of a bit and pretty much every article about it and your every comment on it is objectively factually inaccurate.