Is This Harvard Student Threatening To Stab People Who Say "All Lives Matter"?

Meh.

If a big dude said that, it might be taken seriously. Or maybe a woman who was actually waving around a knife. Instead of a water bottle. But I don't really see it here. 

She seems to be trying to make the familiar point about an alleged error involved in responding to "black lives matter" with "all lives matter." I think there's a decent helping of truth in that criticism...but it's a bit complicated.

I mean, she's acting crazy...but almost all of them act crazy. Crazy is the guiding characteristic of the contemporary left. Though I'm not sure whether or how that affects the argument for the conclusion that she's threatening to stab people.

It doesn't help that violence against non-progressives is a real and common tendency and ideal on the progressive left...

Obviously if someone on the right said something like this, the left and its institutions would freak out...but we're better than them. 

Anyway, I'm going with: not a real threat, though not entirely without some threatening tendencies.