I’d start by admitting that school shootings are, despite being extremely sensationalized, also extremely rare.

There have been multiple school shootings this year alone. Your statement would have been reasonable had you made it in the wake of the Columbine shooting, but to say it today is frankly absurd.

In scare quotes, because the people that commit random acts of violence in schools—versus targeted violence–are so uncommon that it’s hard to draw definite conclusions about risk factors.

That is not relevant. Targeted violence in school isn't tolerable either.

Almost all of them ‘leak’ information in the days or weeks prior to murders; I do think that there needs to be a way to seriously investigate things like that, but I don’t know how you could do that in a way that doesn’t infringe on other, equally fundamental rights.

Indeed, so we're going to have to solve this problem in whichever way minimizes harmful side effects. Unfortunately, that may involve inconveniencing gun owners, but it's better than depriving everyone of privacy and going full Minority Report.

When you get right down to it, a lot of it is an issue of culture, where people feel like violence is a reasonable way to express feelings.

Mass shootings in particular are usually committed by someone who has no intention of still being alive afterward, and they do indeed almost always end in the shooter's death. That's not merely a “way to express feelings”.

the UK and Australia both have combined rates of violent crime–battery, forcible rape, robbery, murder–comparable to the US, and, in the case of rape in Australia, likely rather higher.

You're contradicting yourself. How can American culture be uniquely violent if those other countries have similar rates of violence?

The US does have a sharply higher murder rate though; our violence is more lethal.

Because we have guns.

The unfortunate truth is that you can’t have rights without someone misusing those rights to hurt other people.

Yes, and we preserve those rights despite that because the alternative is worse.

The alternative we're discussing right now is gun control. Is that worse than the status quo? If so, why?

If people can drive, sooner or later someone is going to drive a rental van into a crowd, just because they want to kill people and that’s the way they can do it.

This equivalence is questionable for two reasons:

1. Unless I'm mistaken, that doesn't happen anywhere near as often as shootings do.
2. Cars have a purpose other than killing. Guns don't.