The opt out report is in the specific email that has been sent. Which I understand the logic. However, this information should be at our fingertips with a minimum number of clicks. So i suggest having the opt out report under the REPORTS menu with perhaps options for past emails, all emails, etc etc... this way it can be accessed easily without going on a treasure hunt. And it's more intuitive as well.
Thanks for posting this feedback! Have you tried viewing just the Unsubscribe report clicking the link on the left of the page? Does this not contain the informtion you are looking for?