He did breach basic ethics and standards of professional conduct by his actions, for sure. I would lean against considering what he did illegal, but I think there is an argument to be made that it would be illegal under the CFAA.
It is on the person using code to do due diligence to ensure that any code pulled down in an update is good to utilize. You're seeing an implicit obligation where there has never been one.
In general, most just have the integrity, empathy and detachment to not do what he did, however, any programmer/developer who doesn't have a checklist item of "audit that code" before updates is committing an aggriegious breach of professional ethics;as this is the exact circumstance that everyone should be on the lookout for.
Everyone here assuming there is an obligation on Marak's part to continue to provide an interface in a non-molested form for their convenience are part of the problem. You should have mirrored, or paid the man.