"But on Tuesday, the director of the centre and others received an email threatening a "massacre style attack" if the talk proceeded."

There is an inherit sexism even in the response to this. If this was an email threat targeting say, a kindergarden, or a presidential visit, there would be federal law inforcement coming down hard looking for the source of the email. The specter of "terrorism" would be most certainly be invoked.

Instead we have "enhanced security measures." Because apparently it's not terrorism if the target is women.