Let's say I normally let people cut through my lawn to get to the road behind it. But you come on my lawn and start yelling at my house. So I tell you to leave. Are you still welcome to cut through my lawn to get to the road?
I have no idea. As a non-lawyer, my answer would be yes, I'm still allowed. So the message is "we don't like what you're doing", not "you aren't allowed on this network".
By default, you have no right to be on or use private property without permission. MIT's network is private property. It might be "open" in the sense that MIT liberally gives out permission to use it, but that doesn't mean they give up the right to revoke your permission. This is the same as my lawn. Just because I let people cut through it doesn't mean I give up the right to single you out and keep you from walking on it.
The example you give is an edge case, but I think technically the "get off my lawn" revokes your right to cut across it as other people do. I don't think this is a pretty common sense definition.
