I understand what you’re saying, but as I mentioned above this issues has arisen as a result of the new default watching categories, and how we have our site setup.
There is an argument that we are abusing Discourse a little by using in this manner. This is part of an attempt to drive engagement, which may be a little ham fisted, but I don’t think this is an unreasonable approach. Especially if the unsubscribe process is completely painless.
i.e. you click one link in the email, and your done.