You say that as if that is some sort of an argument. But there is no actual law or force in the universe that says that necessary steps to do something that you consider "securing your network" will therefore automatically not be "criminal". In fact once you start trying to think of what criminal activities someone might take in the name of "securing their network" it isn't that hard to come up with a very long list.
Something does not become legal merely because you have an excuse!
(Note I'm not saying this is illegal or not. That would take careful analysis of the law and probably a detailed specification of what jurisdiction we're talking about and the precise details of a specific hypothetical since it almost certainly goes both ways, depending. I'm just claiming the argument doesn't make much sense.)
If experienced developers don't know about this feature, there is no earthly way that the average user can be considered to have consented to access.
My boss can't kick down my door and ransack my house to find secret documents he gave me. If I violate my NDA, he can seek to remedy that in civil court.
And by connecting to ActiveSync you are telling your phone to "do ActiveSync things" and that includes letting it push policies such as "require a PIN/Password" and "be erased when needed". That you didn't know it meant that is not really grounds for saying it's criminal or whatever.
Hey, you know one earthly way you could know about this feature? Asked. "Hey IT people, can I connect my home phone to my work email? What should I know?".
If you are unable to understand that Microsoft added a lot of stuff to the exchange protocol, and this is one of them, perhaps you are in the wrong field. This is not top secret information, it has been around since Windows CE, and is requested by all big businesses.