In today's climate, combined with everything that's been going on for the last week or so and the upscale of the tension last night with the manifesto, not many positives can come from the decision not to cancel classes. There is absolutely some tension in the law school that was non-existent before today and I would imagine that its exponentially worse throughout the rest of campus.
Not saying I believe that the manifesto stuff is credible or a legitimate threat but if something were to happen today in an area where classes were being held it would be an awful look for the school. It is probably best to be overly safe in situations like this (especially now with all the protesting and negativity surrounding the situation) because if something does happen every move, or lack thereof, will be dissected.