He doesn’t care. The “they include 19 year olds” is just the talking point he’s been taught when those figures are mentioned, because sometimes they’re described as “children”, rather than “children and teenagers”, which means they can attack the data as misleading.

There’s no concious thought behind it, it’s just trigger and response. That’s why they’ll say the same things even when the data is correctly described.

When they do try and come up with their own excuses, they’re usually terrible. I’ve genuinely had one argue that “17 year olds aren’t teenagers” by claiming that when the word “teenagers” was coined, it was only supposed to mean 13 and 14 year olds and we were somehow being dishonest for using the definition that absolutely everyone in the entire world works with.

But they don’t need their arguments to make sense or their lies about keeping people safe to come true because they intend to drag the conversation out forever.

Unfortunately for them, the kids who grew up among the school shootings will vote one day and they’ll have no issue removing the second amendment entirely.